Repair Briefs - Guitar Amplifiers, Band/Stage Gear, A to E

The following are repair briefs for various 
equipment.The infomation is directed
to technically competant repair engineers.Generic terms have 
been used to make this info less model specific,eg terms like 
replace transistor Q123 have not been used.
The equipment is Guitar Amplifiers, Audio Amplifers, Stage Gear.
I would be interested in finding 
any other repair listings on the internet structured as i have 
done ie intended to be less model specific. For convenience using search-engines, 
use keyword divdevrep to target these files.

There is no point in contacting me about any of the following, the 
repair job may have been done 15 years ago .
I cannot clarify or enlarge on any of the following.
In the following V ac means RMS DVM AC volts 
unless stated pk-pk. Mains is 240V, UK

Should the location of this file change please use the keyword "divdev7" in a search engine to find it again

A number of the pictures are now apparently not downloadable, because the hosts have disallowed remote linking although not saying so. To view them , you have to remove the picture file name from the picture URL and put this .htm file name in its place and scroll down to the relevant pic.

Band Amps and other stage gear , A to L

AER Compact 60, made 2000 German made very expensive 60W "practise amp" but well liked for its features. The owner's cat , not a tomcat fortunately, decided to piss on the cabinet. Piss went down inside the Neutrik XLR/0.25 inch socket and also corroded the gain pot so it stiffened up too much to turn properly. Easy enough to desolder the pot, clean and ream out the aluminium corrosion. The neutrik was a different matter, could use the XLR input but not the 1/4 inch, horrible blue-green mess of corrossion inside after desoldering and prizing off the rear. Cleaned out the worst with meths but could only return to normal use by removing the grounding contact that lodges in the rear closure, it would not cleanly make or break and as had been used for months without , in effect, the grounding due to corrosion. As a pin for pin replacement not available in the UK. pinning arangement (I've labelled the A,B,C as not on overlay) A B C 2 3 1 SS S G B,C,1,R,SS,S were all grounded with no plug 2 to ground 1/4 inch S=gnd, A=tip,R=ring no plug R to gnd Also fixed the rather crass foam cover in place with strips of double-sided carpet tape. Technical notes Large Rs 2 x 82, 5W TDA7294, 7815,7915, 2x 7805 33078 opamps, LF353 SSM2142, 470R, SSM2018,LM393,TL072 3x W24257aj-12, HC02A, HC123A,HCT05, AD SD 2115, CS4220 TL072,HCT14 and in all the amp just one tranny K30A incidently "diode" DVM test readings for a good TDA7294V relative to the heatsink 1,3,5,7,9,13,15 .6,.6,-,.55,.6,-,.48,1.2 2,4,6,8,10,12,14 .58,.58,.55,0,.6,-,.49 Akai AMX10 mixer amp, 1999 Dropped then nothing. Surprisingly the latched connector between IEC socket and ps had disconnected, large toroid filter broken away from pcb barely held on by two wires and a crystal problem on the mixer board. ps and amp uses K1181,2x K1179, .15,.22,47K,LT1509 6x 1k, 4x W38NB20, 47k,3x 1M 7915,7815,24M05,7812,78M24, 4x .47,22k 18,10,18,470 ribbon to mixer 5,0,0,0,0,0,5,48,-15,0,15 AKG D1200E microphone Broken wire inside With 120R desoldered and no mike, inductor measured 98R/120R Getting inside , unscrew meshed cover, pull out mike and desolder marking which wire. Pull out the rubber grommet moulding, metal yoke wires internal way round. With piece of dowel , no slipping, or will break fine wire and push pcb out the socket end. After removing socket screws but leave filter sw in place. Used pan scourer as spittle trap instead of perished foam. Alto maybe rebadged Behringer Alto ACL2Pro near enough same as Behringer MDX2200 composer Pro Alto L12 mixer, only 2007, not 2 years old Intermittant loss of one channel , in different positions of the master slider. Undo handles and side plates. Remove the knobs of pots and sliders only, not bush nuts. Undo the 3 front and rear screws that hold top to bottom of case. Break off, with pliers, the hot melt from the headers. Undo the 14 screws from the top, not pcb side of spacers, to remove the main pcb. Beware the trick one under the graphic slider panel, threaded stud so may undo. Remove the main pcb from the panel at the end with the 2 small ribbon connects , first. End-snipping and then grinding off the tinplate tangs before desoldering the active pins is the way to deal with these tiny sliders , without colateral damage. Getting inside, the non-resistive tracks are only 1mm wide and one pair of single wiper "wires" must have been right on the edge of one such track so intermittant contact, 1/2mm transverse bend and repaired. Will resolder the remnant tinplate tangs for earthing and add hot-melt around the housing where there is spaces. 4 tracks inside the 8mm width and 1mm for the conductive track and very easy for the pair of wiper contacts can veer off track. All 9 of these sliders are the same, but no problem with a channel one going U/S unless someone uses all channels, problem was of course, Murphy's law, on the critical one. ps voltages printed on the overlay. Ampeg BA115, 2008 sp 3.5R, mild ? PbF NTC inrush 15R cold No output from bad ground contact in phones so that takes the sp current long pk for XLR Ampeg BA600 - 115 bass amp combo, 6 months old, ROHS, 2010 D-class amps and SMPS Yet another owner forgoing replacement/repair within warranty. I imagine the importer has no replacements in stock as the whole batch has the same faults. Perhaps bass guitarists should use pneumatics and proper compressors to shift air. Mechanical rattle noise due to brass cylinder spacers used over the control pot bushes , loose bush nuts, so rattle. But more importantly At moderate levels an electronic crackle is the main problem. Remove the screws in the cab to release the amp and one caged nut falls into the amp space due to cracked cage. And a nut ( now known) falls out of its cage in the screened off ps+pa section. The PA although supposedly 600W uses only TO220 ,(4 x TOP66 in the smps). Amp and its casing 6Kg but 22x21x16 inch cab and 15 inch sp only 18Kg so maybe part of the problem. TO220 in the PA is 3 on pcb , 3 on one section of heatsink and 4 on another, no fans. As slab SMR nearby are 22R I assume for the moment the o/p devices are powerFET. Each bank of TO220 held down by cross bar and 2 screws. This is my scale of screwdriver torque 1 light finger pressure around handle 2 strong finger pressure 3 fist 4 2 hands 5 wrench 6 impact driver Testing the cross bar screws (they do have captive spring and plain washers) torque measures about 2 , 1 and then 1.5 and 0 The absent one either dropping out unseen as I knew a captive nut was loose inside or still trapped under ps or pa. So I assume silipads had compressed but these are 1.8mm thick porcelain, even less compressible than mica. They were still in place surprisingle but you could slide them with fingers and the TO220 nearest absent screw. This is my educated guess as to what happened at manufacture as absent but distinctive 20mm long bolt not found around here. The 4 output devices should be held to the heatsink via a cross-bar over all 4 of them and 2 bolts thru it into the heatsink. The insulators are ceramic and the 2 central ones, butted up together , do not clear the retaining bolts on their outer edges. After graunching the thread the assembler decided to leave it out and trust to luck one off-centre bolt would hold. Coming to reassembly I found a 3mm screw for replacement but it would not hold, as tapped thread is stripped, so I tapped that one hole out to 4mm. Tried grinding a clearance notch on the side of one pad but got nowhere as ceramic. Not only that but I had no trouble holding the slab in fingers while trying to grind a slot , it was barely getting warm - good thermal insulator or small grinding wheel not generating heat as not cutting into the material ? As possibly BeO , should not have tried grinding into an edge So ,lateral thinking, decided to grind down the screw thread where it interferes with the ceramic , on one bolt. I wonder if this was a one off at manufacture or a whole batch like this, all that was needed was shift a tapped hole 1mm, plenty of room there for that. Or one ceramic pad 1 or 2 mm narrower Unfortunately it would not grind. I assume it was not heating up because the grinding disc was just running over the surface without even rubbing , let alone grinding, so no dust, still the flat edge . Does BeO have that sort of translucent appearance of porcelain? I've managed to grind small sections of the ceramic used is high temperature "chock block" connectors, that has a normal solid white appearance. But given its use here then presumably BeO. It was the slightly milky/translucent porcelain-like appearance that convinced me. I've seen pink TO3, presumably BeO, insulators before but they did not have this transclucent like appearance. I had to get inside that amp again, yet another PbF problem from next to zero insertion force speaker connector at the PA 4 removal & inserts by me was enough , only 6 months old. The slabs pass red laser pointer light, but then on checking but so does the ceramic of high temp "choc block". These slabs are more trnasmissive and scatter the light throughout the slab not just the entry and exit area of the chock block. Complete scarttering with no obvious bright spot directly opposite the entry point. Chock block ceramic was just the adjascent bright spot , much attenuated in comparison to the porcelain or vitrified BeO slab These were not made for the job. They have a hole for either TO220 or TOP66 maybe size transistors . So too wide for this use and the hole is not used . The layout does not mean they have to be 1.8mm thick , any thickness from mica up could have been accommodated. Normally you would go for the thinnest of insulators. Cannot find that 20mm long screw lurking anywhere and extremely unlikely to jump through the grommeted lead ports into other section of amp and then fall out. Straight on , top and bottom x30 viewing of all TO220 soldering looks ok, surprisingly. Did find some nasty rework/fudge. 2 standard radial legged 10uF 50V, C19 and C54 soldered to standard SM pads, no thru board holes. Near it a SM cap, C61 something like 100pF , had been soldered over conformal coating with one end not soldered to trace, as coating under. Owner has owned from new. 4x IRF450N power FET for 600W as D Class operation As distortion was crackle rather than push-pull failure distortion hopefully solder failure , think I can see ring cracks with x30 microscope at awkward angle, pushing around the loose TO220 legs not obviously moving at solder points) rather than some thermal runaway devices. Drilled down deper and longer 3mm bolt for the missing one eventually. Laid heat resistant glue over pairs of starwashered bolts and along the cross-piece to definitely lock in place. It does use 2x Int Rect IRS20955S, each one driving a pair of FETs and there is an IR application note out there for those being used in Class D. That would explain the socking great inductor/choke well out of scale with all the SM on that board. Will check that inductor is at the output and try and locate a clock line , presumably back to the SMPS. A generic problem with these will be mechanical noise from vibrating control pots. 7 of the 9 were loose , in 6 months of non-commercial use. Not brass cylinders over the bushes but are stop-ledged/ partial threaded leaving not enough space for chassis thickness, nut and normal star washer so they used thin plain washers. Luckily I have managed to fudge some thin star washers, too small inside diameter but I belled out , using a tapered shaft nail punch to slide over and tube to push down on, to go over the bushes - to remove would require inserting dart point and rotating off. Downloaded the datasheet and that IRS is for pwm/D class operation. Input ,pin3, goes back via Q9 to 74C04 buffer so digital. That large L , in a 53x53x24mm case is connected between the common points of both FET pairs and across the speaker (with an ohm or so somewhere not ascertained). That L1 measures 4K ohms , inductance not possible on LCR meter as a yellow block HV polyprop? cap , label obscured by L1, is also across it but measures 1.15uF apparently on LCR meter. Speaker lead has a 4 pole connector for disassembly , 2 poles per wire, but same size connector on the pcb only 1 pole each. Worse than that the commons traces going to L1 are 3mm wide with solder run thickening for the current but the 2 output traces going to the speaker are 1.5 mm wide and plain tinned. So assuming 300 watt for a second into 4 ohm then about 9 amps. From the Enumber in, it is 1 oz board and using for 60 mil track and 9 amps for plain copper then 100 deg C rise , don't know how much the tinning coat would change things , say an unlikely doubling to 2 oz in effect, then 32 deg C rise , unacceptable ? Can you have the bridge of a bridge tied D-Class filter of form insted of --L--Sp--L-- as single L and speaker and C in parallel |-----Sp-----| ----|------L-----|------ |-------C----| L is inductor ,Sp speaker,C capacitor I'd forgotten the double wound toroid inductor of 360uH in series either side of the speaker. What sort of value of inducance for L1 and its wire gauge/current carrying requirement for 300 to 600W use? C 1uF, 250V I removed the filter cap to measure the inductance of L1 . Cap marked 1uF, 250V. This L1 weighs about 170 gm, estimating weight of remainder components and pcb from total of 290 gm. Through a hole I can see some wire about 1mm diameter. Using 1KHz RLC meter, L1 measures -2.2H on H scales and -140mH on mH scales, don't know what that means , will try and find a manual for an Avo B183. Maybe faulty, but measuring plain inductors through the scales is positive and consistent across neighbouring scales. 1KHz ac resistance is 230R, DC resistance is 4K so perhaps what is labelled as L1 is R and L in series. Perhaps R of 4K and L of .6H , to give 230R at 1KHz, but if wholly 1mm wire I cannot see how 600mH with 170gm of 1mm wire, strange core material? I could not find a manual for the B183 or B184 . I tried an audio output transfrmer and a resistor but no negative readings on the meter. Perhaps there is another capacitor inside the can , other than this external 1uF that I removed temporarily. It almost seems perverse, 0.4 amps of mains current draw (at 240V) and 25 watts of 400Hz sine into 4R dummy load and a thermometer laid over the tabs of the 4x TO220 output device, rises only 8 deg C over ambient. And that with amp laying on bench so no convection over the external heatsink vanes, no wonder no fan needed. Previous D class I've played with were Stagepas , not possible to monitor their operation without making up umbilicals to operate PA out of the little box. And as separate clock maybe "RF" problems doing that Do Ampeg make bass amps? There will be loads of returns of this model. Any large lump inside a bass amp is likely to vibrate if inadequately secured. That 2 x 2 x 1 inch lump is only secured by its screening can at 2 pointsplus inductor ends soldered. That was the main problem , proper solder would be hard pushed but PbF only lasts 6 months like this. Also PbF failing on the speaker socket, would not have been so bad if they'd used the 4 pole connection like farther down the speaker line and bad PbF on V2 of prea. Plus the absence of star washers on the pots. Ignoring the absent h/s bolt. PCB construction of the PREA pcb , where holes are drilled for thru-board components but of diameter far too big , thru-hole plated , but no eyelet/inserts used to fill the gap. So 1N4001 size leads in holes twice their diameter and 1N4148 in holes twice their diameter. So not a case of only one drill size for all. So in area terms about 1 to 4 ratio of lead to solder. Bad enough practise with proper solder but with PbF, ring cracks starting all over. Is it to avoid mutiny by the by-hand board populators ? Loads of suspect looking possible PbF ring cracks on th ePREA To get the amp out of the cab. 3 screws each side. Thin steel rulers either side to release amp from cab. While at it open out the 2x pairs of holes in the cab , drilling through the wood, to make alignment of screws easier. To release PA+PS cover 2 rows of smallest screws and 2 countersink at either end. Broken caged nut, small size cages. Found replacement 4mm caged nut but too large for the existing holes. Ground back one arm only of the spring clip to get into the square hole, the other into gap between cover sections and stopped it shifting out of that gap with hot melt glue in there. Replacing amp in cab hang top 2 bolts first, rear flush with cab sides and heatsink recessed about 2 or 3mm inside cab line. and lies with about half inch gap under to the cab ledge. 2 sheets of celluloid at the bottom helps reassembly Mains filter section TH1 cold 8.2R. R66 and R72 measured 330K, markings 750K ? PREA 820R, 10K, 4x 10R , 2x 100K?/R? large Rs PS 10,1L,3x10R ?, 47K,22R,2x 68K PA empty pad has no chassis pillar under Maybe ringcracks on 2x TO220, under x30 mag. Speaker 3.7R, consistent at all times so hopefully PbF in there not playing up. Power level control/crossover each lamp 1.3R and inductor about .2R PA 7915, 7815, 7812A TIP32C, TIP31C LM35DT temp monitor, 4x IRF540N 74HC04, 082, 72, 293M, 4580M, 339M VTL5C7 opto coupler U21 E78E 805J89 C19 , C54 10uF, 50V soldered to SM pads Black sc 5 short and 1 long (to SMPS Tx cover ), 2 medium length for SMPS Al angle plate. C61 soldered thriough conformal, one lead to o/p FET common, S of one D of other. Other lead to 10uF (CBS) to pin 15 of IRS.. R25, R26 01C = 10R, C1D = 8.84K In cct with RLC meter ,measured 1.43nF over C83 and with C61 replaced with 120pF measured 1.53nF so perhaps C61/C83 is about 47pF. I managed to overcook the original on removing and did not fancy removing the other one just to measure out of cct. Full mains ps V at sockets pa W -44V, Y -25, Bk 0, Be -44, R 44V prea R -15.2, Bk 0, Be -15.3, Bn 13.8, Y 302V prea to o/p 0,-15,15,0,0,0 0, .4V, 0,0,0,0,0 4R dummy load, note not ground referenced 400 Hz output 10V ac over 4R for 46mV in with all controls at mid and vintage ch. About 0.4 amps mains draw and only 8 deg C over ambient for thermometer laid over tabs of op TO220 considering amp laying horizonttal with h/s under Access to speaker wiring removing RH side (from front) hives horn access as well. Dart point in corner and lever will remove front grill panel off the velcro pads, leave labels in place. Rustle noise above a certain level and then continues on reducing volume, feeding in 50HZ. When good 3V across speaker but with rustle 2.9V say. R-C across speaker brown polyester cap and 2x 22R 1W sM in parallel for R Bad solder joint at pa speaker connector (2 pole only) and trace on upper side of board , lever up shroud enough to introduce solder while heating from below. Bad solder at L1 to traces, while resoldering fill in the missing solder thicknessing over the traces near the ends. To brace this large L1 decided on a solder tag introduced between PS Al angle and chassis using existing bolt through. Length of pen barrel with hotmelt in either end , one end slotted to go over solder tag. Other end build up with hotmelt into hole in L1 casing, hoping reduced ventillation? not significant. With 4 wire prea-pa lead missing, very little hiss from speaker. Still rustle noise above a certain level. Turned attention to prea. Amp would work fine laying horizontal , put back in cab and play up. Probably bad PbF at V2 socket as that area sensitive to twizzling , fine with 12AX7 vertical but not horizontal. Replacing V2 made no diff. Remember double sides so solder points both sides. Opto coupler soldering looked bad also . Redid all large R and C on both sides. Ampeg B1, 1992 Blown transformer due to shorted op device and TIP device broken pull switch spindles repaired as PTF. 2x MJ15001, 2x MJ15002, TIP31C, TIP32C, 2N3402, 2N3440 220R, 10R, 3.3R 2x 10R, 100R, 2x 1K, 4x 0.33R 24V fan N/C th sw 2x 5532 Arion (Prince Tsushinkogyo) guitar tuner,1985 Not chromatic (new one on me) ie not full spectrum , does not have pitches "C" and "F" , dedicated to guitar use. Bad on/off, probably lead/jack trodden on and broken solder on socket joints, no nut mechanical holding of the bushes through casing Ashdown maybe worth checking Trace Elliot, Orange or Peavey as related companies Ashdown ABM500 bass amp, 1997 Farty noises Had been seriously dropped in a flight case and a number of problems, now sorted so it now works but there is a fairly low level background hum problem with no input. Attending to all the pots as most were worn or suspect in some way and some solderings at the heatsink. Festoon bulb replaced with a physically larger 12 V bulb so mount needed extra fixing in place, o/c voltage supply, has dropper, at the bulb mount 17V ac. Some other data secondaries 13.5V; 62,0,62 ; 17,0,17 ; 270V (16 ohm DC ) main ps , +/- 84V Thermal sw n/c. 1V dc over meter reads "2". At 22 deg C , the heatsink thermistor , in circuit, measured 70 ohms giving only 9.6V at the fans, parallel with 68R gave 11V and 28R // gave 12.3V. To remove the preamp board, remove pot and switch knobs and push in switches and slacken off the transformer to give space. Shift the other way to remove the rear board. See tips files for coachbolt removal problem. All inputs and outputs and pots (exept the pot casing) are electrically isolated from chassis, on schema and in reality. Just the mains inlet earth bond point to the chassis. The pa has a nominal "grounding" point of // 100nF + 10K, 1/3W R and the pre has the same to chassis and the signal line "ground" between them. Another sort of problem with this faux ground arangement. I thought it odd how long it took to drain the 450V caps and the main reservoir caps, before I previously dismantled all the boards. You have to connect the low ohm resistor to faux ground rather than through 20 say + 10k//10K to real ground. So about 5K between real ground and nominal ground. Disconnecting the signal lead, the pa o/p is clean. Driving into 8 ohms , with shorted inputs then at max volume setting then 0.7V on DVM ac range, dropping to 0.002 V for min vol. It is more intrusive than I would normally expect but I don't have any figures for what is normal. shorting the preamp 10K then the hum goes. The input 1/4 ins shorting contacts, with no input jack, are ok Putting 1K across the pre amp 10K then the hum level drops to a much more acceptable 0.1V. What are the safety issues with this sort of arrangement ? They are not marked on the schema as fuseable resitors nor on board marked ! in a triangle. I've probably found the source of generic hum noise problems in Ashdown amps with this faux ground structure. The problem pot marked with a "B" meant it was linear and not log so a replacement easily found. Taking the original apart there was no broken track or rivet /paxolin failure, stressing/bending paxolin and measuring etc showed nothing untoward. But I did notice the track was offset, ie not coaxial to the paxolin base. The noise intrusion was most prominent at about 2/3 and at that point due to the off centre track and slight ovalling of the outer pot casing the track/wiper at this point was very close to the casing. For the replacement pot I bent back the four tangs that hold the middle casing/housing section of the pot to the bushing plate, introduced four bits of insulation, closed back on them and glued in place. So the casing is now isolated from the spindle and bush which is still properly grounded to the chassis. Now normal hum level with shorted input and maximum vol/gain settings varying from .04V clean to 0.07V ac on full grind setting into 8 ohms. So factor of 10 or better improvement just from isolating that one pot casing and presumably more centrally aligned pot tracks perhaps to lesser effect. The 2 x 10K faux to ground resistors still as the original design. One of those annoying self-made, in a sense, problems also associated with the faux earth. Trying the amp with the equalisation board free of the chassis was fine but mount it back in and horrible mains noises. To save messing about I was temprarily placing the board back in without the 3 spacers on the 3 pots. These pots have the casing to chassis earth but the 4 slider pots have the cases connected to faux earth. Without the spacers then the slider cases came too close to the chassis. The grid vltage on the ECC83 varies from 0 to -3.8V via the clean/grind pot I wish there was a proper techie/muso translator somewhere ,ie full translator techie-speak for techies and muso-speak for musos . What is grind ? in terms you can see on an oscilloscope for instance, not the usual muso speak. I want to know, in this instance, if you feed say a triangle wave in what comes out on full grind? Final loading check , 400Hz, giving 20W in 4 ohms, no rise or drop in Vac over test period. Heatsink with the 2 fans active gave 20 deg C rise over ambient of 22 in 12 minutes. Also into 4 ohms, no input , clean channel full vol & gain of 0.03V ac of mains hum over the load Ashdown ABM-500 EVO-II Head, 2002 Intermittant crackles and gain dropping, part into a set with normal usage. 2 temp sensing things , one vaguely touching , the other bent away from the heatsink. Perhaps every roadie should be put in a flight case and dropped down some stairs as a lesson. Anyway both heatsinks must have bent relative to the pa pcb, bending the leads , when dropped. Main spring held items stayed ok. How to anchor back more firmly than just white paste? The main TOP66 power devices etc have those slide on spring steel clips but the loosened TO92 tranny and fan thermistor are a long way down from the mounting slots, for anything like that. Any ideas ? - live heatsink btw, hence not rigidly held to body. Too crowded to drill/tap the heatsinks and the assembly of these sort of hook-clip arrangements is realy make once, dissamble/reassemble at your peril. This is a likely generic fault scenario for all such "live heatsink" amps that are only fixed to flexible polyester pcb board Double sided foam/tape tape was supposed to be keeping a duaghter board marked EB SUB ? (4013 and 3 x 072) fixed to the preamp but dislodged in the same drop presumably, failed solder joint/s leading to crackles. I removed 2 nearby caps , 2 small holes ,to match cap pin spacing, in cut down lengths of cable-tie , and soldered back in, regooing and positioning the 2 shiftees. Volume was fading down after half hour of use, presumably because the NTC fan thermistor was staying at room temp and fan speed not upping with increasing heatsink temp. Unsupported daughterboard is now braced back to 2 chassis anchors NTC thermistor TH1 ,88 ohm cold 2.2K,4.7K, 1W, 4R7 vitreous 33R , 1W on prea board main bridge rect , one prong poor solder, supply pcb conn block for fan , bad solder. Returned for "repair" years later , dead at power up, repeated pressing of "Mute" made no diff. As received , no proiblem, added 2x silicone sleeve plus2x Hamma beads to the Return Tip bypass sw as the compact type and next to impossible to clean. Made a slot hole in the pcb between the Send and Ret so, and wired across to replace the cut trace. Returned some years later. Failed , no output, after using in/out leads at the rear. As compact , tight footprint , and difficult to clean sockets. To avoid blanking off and making a new chassis hole. Drilled through pcb at the common trace , so wired in a replacement. Then doubled up silicone sleeving and Hamma beads to reinforce the sw action Ashdown Acoustic Radiator 2, amp, 1999 It was only when I saw the IEC on the rear that I realised it was not 1960s, scuffed red mock leather covering, large thick leather handle, "ivory" knobs , that cream stove enamel used on a lot of medical kit etc of the era after the crackle finish of the 40s/50s. Now I've seen it all. To get the amp out you need to remove a speaker to release the speaker wires internally. But its a dummy speaker, presumably the 2 in the model name means 2 speakers. Basket , suspension , kevlar looking skirt, and cone , only. No pig tails or holes for pigtails or Voice coil or magnet. So if these were off a production line, how were they further processed? 4x3 sets of holes in the basket for what I would have thought were screw holes for a magnet , but sealed off by the seated cone. Would they glue in VC to the cone and magnet glued in to the basket with some sort of active monitoring of sound output , while posistioning in the uncured glue? Problem is the otherwise Ashdown Bass amp common symptom of loss of output , returning a few minutes later, but this one will then continue for an hour or more with no drop-out. Not had a chance to power up yet , to investigate Never seen dummy one before . I've seen holes in boxes called adiabatic resonators , yes, so I'd believe anything was possible. What is an active loudspeaker , if not an acoustic radiator? The company blurb refers to 2 speakers which to my mind implies 2 of the same sort of speaker . Eiter 2x active speakers or 2x passive speakers which would likely result in a lot of returns Tweeter 4.1R, bass 4.9R 2x lm3886t (slide the spring H/S clips) Remove front expanded Al sheet and reset the dents and restress with weights and add hotmelt glue runs against the frameing Brass sc to retain the amp RH sp is dummXover wires are close to shorting cut sp wires and add terminal block open up hole in the wood for sp wires Active sp marked cone 20 2015 D9 1?99.78 and barcode on magnet 0600 300865333 added tap washer under the bare sc only just holding the handle to the cab, as original broken Jack in tuner F/S will kill the amp, or into S or R will seriously attenuate the amp. Setting I was in , pulling the vale made no vol diff bad low i/p so, scratchy Tube pot. Lot of bent pot shafts Whole board under the digital pcb loose from the chassis , all nuts in place just Chassis rear is meant to have those wonky angles. knobs LLLLSSL LSLLSSSL Q pot pulled out and bent Discharge the 450V caps , 250V on one 2 days after no mains Discharge at R31 and 38 solder ring crack at .25" so tip Made replacement stem for the unobtanium quad pot Taiwan alpha B 100Kx4 1.5mm thick Cu strip 45mm long and ground down to 3mm wide at interior end, protrusion knotched to take dollop of hot melt mid pot posistion, outer pair measuring 48K , inner pair 21K. Cu strip should have been 1.9mm for a tight fit rear level pot loose some 1/4 in so bad solder all sc terminals for power could be tightened replaced the XLR 292V and 276V on 400R and .7amp mains current at 240V and V1 glowing dull red replaced V7 -13V on R63 bias Tank 57R in , 210R out steel grounded on o/p side Background hum increases with reverb pot from amp short lead has ground shield wire to R25 RMS noise .4V ac with R6 , no i/p , over 8R / .024V ac in the correct way round . Long lead to Tx end Replace meter, then graphic panel with lamp at meter, then main board . With less than 80% mains then a Jacob's ladder buzz Something bad about lowZ Z socket, middle contact required to gnd with a mono jack. With stereo jack low level o/p with tip and sleeve, needs the R-S connection for full o/p. So 2 chances for 2 contact failures , although no bypass contacts used. 75mV of hum when amp is placed inside the cab, added mu-metal draped around the Tx, reduced hum to 50mV (25mV when out of cab) 2x 150, 2W 2x 4.7 , 1W discoloured to white blue gold , 2.7R on overlay Ashdown Electric Blue 180, MAG250, 2004 IEC inlet broken and fallen inside along with the line socket. Replacement IEC plus fuse needed 2 screw holes ball-milled into the steel . Discharge the H/S s before undoing PA pcb screws usual suspects under and lacquer on the sc Ashdown Electric Blue 180, made 2004, 26Kg The amp cut out totally and when it had cooled down and he switched it on , it worked, but he noticed the fan was not turning so he switched it off again. Beware the heatsinks are not grounded and +61V on one and -61V on the other. The supply to the 12V fan is off the preamp board so had to remove from the front pannel. The owner had never had to tighten any knobs but one grub screw (brass) had been graunched at manufacture so had to drill that out first (see the tips files for technique). The 100 ohm dropper to the fan had resonated and failed inside the pcb hole, copper coloured fracture face so presumably work hardened copper failure. 150 ohm dropper in the display area had overheated to 156 ohm and giving apparent band colours of brown black black. Uses 2SA1668 , 2SC4382 2068, LB1443, 5x TL072, M51134FP 2x .33, 4.7, 4.7K large Rs Speaker DC resistance 5.6R Ashdown Mag 200 Bad intermittant throughput, but not wh me, of course, all good. Bus as bad in either input, probably bad EQ SW and also changed axial type RETURN so. to conventional. After replacing the EQ sw with a standard toggle sw and wiring into place, (opened out star circlip to seat centrally in the too large panel hole), turned out was due to bad solder at a cap connected to the sw , close to the sw. Then further problem of no output, due to bad solder on sp output socket, both were bad Ashdown Mag 200, 2001 Bad no-name input 1/4 in so, or pehaps bad solder pad. Cross-coupling meant problem on one would affect both inputs. As a pot shaft was bent , perhaps the cab had taken a bash. Tip contacts bent or misplaced. Replace 2x 1-K with longer leads so can bend out of the way of replacement conventional wired in replacement so. Effects return so is switched but its gnd solder point was bad. Tx 1-.5R// E 2.5R, O 2.6R sp 6.4R Remove 2 front caged nuts before removing the Prea pcb 2x 56R resoldered as heat browning Remove the copious dollops of white goo Tape over the input socket ends , while some hotmelt is molten between them and the pcb while placing in the chassis. When cold, demount and add more hotmelt around the pins. Wiring to one so, around pcb edge and a hole made in the pcb for the other so wires. Ashdown MAG 200, maybe 2000 or 2002 Combo with 1 x 15 inch speaker. After hour of use it cut out. Next time it failed after 10 minutes. Lead-free solder "volcanoes" or electrolyte from the 10uF cap near the J112A N-D type FET caused solder failure on the cap and falsely triggering the protection circuit. In use voltages on the 112A were 0.2,0,-8V clicks over at about -1V As mosfet, discharge the reservoir caps before dismantling if no speaker load. In working order the Source to ground of each power fet shows a forward "Vbe" one way or the other and only that terminal. To get to the front board leave the 4 nuts in place and remover the 2 captive nuts and the 2 small screws on the top. To replace put the sleeves into the front panel rather than on the pot shafts and locate the meter into recess before pushing in the pots and switches and sockets. The thermal switch T'-key 125-a15 code meaning 125 degree C, I took to 120 C and did not change state and not mechanically suspect. Also 3 of the pots were (needlessly) long shaft with nothing other than paxolin and nylon bearer around shaft keeping them in place. Could easily have used the normal shaft ones and extend the pins, so proper bush nuts to front panel could be used. Replaced with a panel mounted one , wired into the board. Meter had been pressed in and soon would have had solder joint broken. Made a hole through the pcb for a nylon bolt and nut glued to the component side of the board so could be tightened against the meter when aligned and fixed in the chassis. I do not know if this is correct setting but this VU meter was 0 on scale with 0.18V RMS 1KHz input from a 600 ohm source and input pot at maximum. I don't know what the illuminated meter looked like as original but I reckon my re-jig would be better, looks quite nifty, although not 'retro'.
 Ashdown Mag 200 meter mod
 Ashdown Mag 200 meter , side on
Because the cover protrudes 1mm or so it even looks effective when viewing skew-on. Put a 2K , 3W dropper in and a bright blue LED wired-in and moved to vertically under the meter movement when mounted in chassis and angled toward the ring section, so internal refraction , through the plastic, forms a blue ring around the ali cut out , especially after abraiding the coating off the aluminium in that recess, plus a bright spot under the meter that shows in bright ambient light and it also throws a light on the scale. Filed a small notch angled downward so the front periphery to the meter was still circular but allowed more light into the bottom area of meter cover, revealing more of the LED directly as an indicator for bright light conditions. 2 LEDs , under but angled in and across, would have been better as the static part of the movement shadows part of the light cast. Comment on return to the owner. "looks amazing! thanks for doing that, it really makes it stand out, cheers" The 20mm fuse on the preamp board is too close to the metal edge so covered with a cut-down piece of wide flatted-U file binding spine. As all lead-free solder redid all heatsinking joints on both boards.Main AC rails 50-0-50 and preamp 18-0-18. Ashdown MAG 300 amp, 2004 meter movement but no output, no hiss Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal failure of this bridge, dodgey looking splodge logo, presumably Fronter logo and 8amp rating, marked AC BP8-04 or something else to change as well? Main caps look ok and ESR (for what its worth in such cases) ok The 2 failed diodes are -ve to AC +ve to other AC Suspiciously 2 solder points look like crazed PbF solder but all is SnPb, melted and reformed? the 2 points are at the -ve terminal and the AC terminal of the other failed diode. Output devices DVM-D cold test as expected. No heated traces or even obvious gaseous eruptions from the bridge or anything out of the normal. No reported preceeding noises prior to failure. Looking at the Frontier datasheet, the bridge has to be derated to only 3 amps at 40 deg C, which seems surprisingly low temp. This amp was all day sitting outdoors in the cloudless sun and failed after 1 hour of use in a set. So 40 deg C was quite likely exceeded, so probably the reason for failure. As constricted in space , without going off board, I see a heatsink being bolted to the replacement same rating bridge, or wiring off board and bolting to the chassis I cannot see how an honest rated 8amp bridge could be in a 15mm square pack. Replacement will be 4 amp 200V rating, with a hole to take a vaned heatsink, no hole in the original (perhaps to get 8A it uses the central area). The fan airflow in these amps is fine for the output heatsink but the bridge is sheltered by the main caps and wiring knot, vane will be off-centre poking into clear air, off the edge of the board I picked up the wrong bridge, the original Frontier one does have a central hole with 4x10" cab, combined sp imp 5.1R no fixed DVM-R or D at sp outlet 8AC6 = 35430DEC tighten and lacquer sc under h/s. Tied the vaned h/s bolted to the bridge, to chassis base -70V on outerh/s , +70V on inner one returned to owner and bounced back -25V on outer H/S, 0V on + h/s Both fuses blown softly , after 1.5 hours of use and volume turned up. With catastrophic failures I initiaaly down rate fuses , in this case to 3.15 amp but forgot to replace them with 5 or 6 amp ones PA overlay marked EB150 , T5A 36V MAG250 , T5A, 45V presumably AC, as MAG300 is higher V then assumed 5 amp were correct value instead of th initial 6 amp. If 2x 5A blow then 6 amp ones wil lgo in there (NOTE to myself , next time some bright silicone rubber rings placed around such testing purpase down rated fuses, next time ) Noticed C15 and main cap C16 both had marks from abrasion or perhaps discharge. REmoved C15 and added extender and reorientate , on end, to clear the main cap. Sp leads have anti-shake spades , push to release Ashdown MAG 250 For factory retro-fitted fans. 4 faults in one just fitting a fan and power bleedoff For random fan stoppage - look for Instead of 47R 5W W/W placed in line with the fan (dangling R unsupported at one end) , 0.047R soldered-in so 21V across the 12V fan. Surprisingly thousands of hours of unproblematic use like that. Even without that , for any long term excessive wear on the bearing of fan , the reaction force pushes the impeller towards the mounting bracket, eventually touching it. You could see a slight trace of where one fan vane had rubbed the bracket and rubbed the plastic of that vane, ie clear of usual gunge. If meter cover stays in fascia cover to protect when working on prea. Replace with 47R, supported by tagstrip bolted to fan, and new fan with the centre section of the mounting bracket hacksawed out. Take negative lead via a wire to an added terminal set in the prea. Fourth mistake : the fan just circulates the air internally, no added baffles to duct air in from outside. Set the fan in a stiffened card bafle going from LH corner of front to centre divider of rear vent. So air heats up, softens fan's plastic vanes , vanes flex a bit, to the extent of touching the mount. Removed the the sw and checked for temp action and any vibration sensitivity and checked caps in the controller area. If the sw goes o/c in these Ashdowns the gain drops at the top end mainly, not cut out . 1KHz in and 1V ac over dummy load then if sw changes then o/p drops to 0.04V ac, less so for lower frequencies which seems upside down for amp protection. Still random intermittant gain drop and distortion. Beefed up return socket switch as per tips. The holes and pads for these are far too big for the pins so a good place to see crcked solder, but not this one, so far. R46 , 1/3W, resitor at the 1.6K bias R cold joint. Ashdown MAG 300 amp, 2004 Both 6.3amp fuses blown, 2 diodes of the bridge rectifier s/c. Internal failure of this bridge, dodgey looking splodge logo, presumably Fronter logo and 8amp rating, marked AC BP8-04 or something else to change as well? Main caps look ok and ESR (for what its worth in such cases) ok The 2 failed diodes are -ve to AC +ve to other AC Suspiciously 2 solder points look like crazed PbF solder but all is SnPb, melted and reformed? the 2 points are at the -ve terminal and the AC terminal of the other failed diode. Output devices DVM-D cold test as expected. No heated traces or even obvious gaseous eruptions from the bridge or anything out of the normal. No reported preceeding noises prior to failure. Looking at the Frontier datasheet, the bridge has to be derated to only 3 amps at 40 deg C, which seems surprisingly low temp. This amp was all day sitting outdoors in the cloudless sun and failed after 1 hour of use in a set. So 40 deg C was quite likely exceeded, so probably the reason for failure. As constricted in space , without going off board, I see a heatsink being bolted to the replacement same rating bridge, or wiring off board and bolting to the chassis I cannot see how an honest rated 8amp bridge could be in a 15mm square pack. Replacement will be 4 amp 200V rating, with a hole to take a vaned heatsink, no hole in the original (perhaps to get 8A it uses the central area). The fan airflow in these amps is fine for the output heatsink but the bridge is sheltered by the main caps and wiring knot, vane will be off-centre poking into clear air, off the edge of the board I picked up the wrong bridge, the original Frontier one does have a central hole Ashdown MAG 300 , EVO 2, 2008? sp 6.2R intermittant cutting out, banging the cab will reset for a while. pa +/-71V on the heatsinks + one nearest Tx . Discharge the main caps before dismantling, regardless of whether last used with speakers or not. Top thermal sw n/c There is a bang preceeding siilence and another before returning to normal. Stick pierced cloth tape over the caged nuts to avouid tearing up the lining shield foil. Beware of pushing the meter front when replacing amp into the cab. The sp cable is squashed to accommodate sliding into the cab. ring cracks starting at sp outlet. inadequately tight 8sc on PA pcb , added lacquer. Bad plating? on Harwin connector pins , 100 percent tin plating tinpest problem? Because of the sharp edges to the tops of the pins I would haveexpected any pbroblems with the plating to be on the socket pins put plating there is fine as is the crimps Added RTV to major PA components as can rock easily Resoldered C5, C8,C1 on PA in case of false protect mode weak fuseholders Ashdown MAG 300, 2004 pcb marked MAG250 EB150 Blows mains fuses during low volume practise session. Survives long enough for the meter lamp to come on half a second. Nothing found obviously suspect in ps or pa probing around cold and inspection. Bad internal AC supply fuse holder contacts , arcing burn marks on the fuse barrels. Both are 5 amp rating but neither blown or showing stress on the fusewire. So much for so called "Top Cheers" transformers. Initially could take variac to 50V and then run away , now cannot even put the minimum of 5V on the primary , with nothing connected to the secondaries. So just coincidence of bad fuse holders on the 48V ac lines or directly leading to failure ? Could repeated breaking of secondary current induce very high voltage in the primary leading to shorted turns? Nothing visibly wrong through the tape wrap or smoke trails from inside. DC measurement on primary now about 1 ohm , unpowered, was about 6 ohm when received. The first winding was the low current 15-0-15V secondary. This was wound with doubled up .45mm wire in one go so reducing the number of shuttle passes to wind on. The 2 wires brought together to form the "0". Thought to myself, perhaps that is ok for low voltage winding as only 50V peak or so maximum for 2 thicknesses of lacquer to sustain. Then the 3 amp 48-0-48 wound as 2 separate layers of 1.06mm wire, not run as paired winding, fair enough. Anyone know why 3 runs of loosely packed turns per layer when one run of tighter turns per layer could have been done, so avoiding overlaps? Get down to the unruptured thermal fuse, tails of the primary and the .7mm wire primary and nothing obviously wrong in the way of hot spots. But blow-me-down a return to the paired up winding and ends joined to give 120-0-120V for 240 UK use. But of course now 2 thicknesses of lacquer having to sustain a normal maximum differential of about 350 volts. Totally wound off and the small burn patch was midway , where maximum voltage difference is/was, so just required some otherwise rather minor, short duration, mains voltage spike to puncture through. Thermal fuse marked Klixon ? 17 AM 033A5 M4 AB From not fuse but bimetal dome switching on combined temp and amperage maximum 8 amp , take the 3 digit number , if starting 0, subtract 7 and multiply by 5 so 033 == 130 deg C for sw temp. If number >060 subtract 40 first, if >160 subtract 140 first, if >200 subtract 180 first speaker 5.6R Difference on cold probing between drivers on both sides of the amp due to resistance 47 + 330R between B-E of C4387/ A1668 but not corresponding ones. If gingerly powering up this sort of amp don't have a speaker connected as amp is unbalanced below about +/-25V. Powering up on bench power supply and monitoring output line +/- 10V o/p 9.9V +/-15 o/p 12V +/-20V o/p 18V +/-25V o/p settles at 0V Uses +/-70V 2x 2SA1294 , 2SC3263 Output pot goes past the endstops, dismantled and reformed the outer case. Meter on this ashdown stuck at the top, needed desoldering off the pcb, measured 650R and read 80 percent on DVM voltage, unstick the tape before resoldering. Ashdown Mag 300 No output after someone replacing the fan and not discharging the main power rails at the o/p device heatsinks. Touched one of the fins to the prea -ve power rail. Shorted the -15V zener and at least one of the 072 IC2 / IC3 . As received static 0.43V over the meter . Replaced the zener but problem with the bass pot so that above 1/2 then distortion and then cut off. -11V on pins of the ICs that should be about 0V and varying DC on the tone pots. Ashdown Peacemaker 20, 2003 Loss of preamp, pa ok with external feed 0.05V 400Hz ac into return produced 3V ac over 8R , "maximum " volume set. Signal injecting at pin 6 of IC2 and IC3 produced o/p 10K dropper failed in valve anode supplies. No obvious reason for failure , even breaking open, no overheating or colour change to body or bands . Replaced R11 and R23 also o/p tx 0.9R R90 22K replaced with 2x 47K , 10K in the schematic and A1=A2? To refit main board , and 1/4 socket spacers, 3 each to the front and 2 each to the rear Ashdown Peacemaker P60 valve combo, 2003 Volume fluctuation and background rustle I discovered how to get into it, remove front knobs etc and remove the facia panel first. Lever out the mains switch enough to pull the fascia around it. Remove and replace amp with cab on its side. Meter unslots and tape it to the underside of the chassis. This amp runs very hot in the region of the EL34 output valves, almost to the point of charring the pcb, localised black rather than just brown discolouration, through the bulk. The valves are inverted and no ventillation path under or around the valve bases. There is plenty of space to mill holes in the pcb around the periphery, and avoiding traces, to allow some ventilltion through. Scraping back some of the pcb surface browning and into the bulk of the pcb material , the browning extends the depth of the material. Also some brown staining on the surface of nearby solder points, probably some vapour coming off the polyester and settling on the solder. No ventillation grill in the cabinet top either. I'd half considered a fan but there is no obvious place to put it and without cutting a hole in the steel chassis or the wood cabinet it would just be circulating the air, unless mounted outside the chassis , directed over the bottles. Could use the rectified heater supply as a less than 12V supply for a fan. Cut a 3 x 2 inch hole in the cab top , masked with grill. Positioning it asymmetrically off-centre in both senses so above the big bottles and clear of internal encumberances so a 2 inch fan could be fixed under the grill , later, if required. Bolted down some metal bar etc with the handle bolts to form a slideway, for 45 degree drill bit guide to slide and step along to cut 2 angled slots to bring the vent hole inside the chassis. Cut through the ends and tidied up and painted black. And the pcb perforations with dremmel and 1/8 inch ball mill Putting a thermometer in the quiescent vent flow, 40 degrees C above ambient, better out than in. On EL34 side of one AC coupling cap .25V ac dropping to about 0V and on the other side .25V upping to .3V on volume drop. Replaced that one nearest the heat build up and its match. The pair of 220K in blacked glass sleeving to -12V is to " stablize the bias until the tubes have warmed up enough for the self-bias to take over. It adds about -6 volts to the grids" soon after switch on. One HT cap had bad solder. Replaced weak input socket. Beware earth continuity is through 1 only pcb standoff and beware of trappping loose wies against standoffs. EL34s use ac on heaters, 12AX7 s use +/- 12V DC in pairs 33K large dropper, bad solder points and overheating, stood off the board with heavy duty pins, also 2x 1K, 2x100R, 1K. 2 canted 072 because of large Cs. Mains 7R // 29.5R,.2/.3R,.3R o/p 113R bn, 103 bk,// be/gn .9R, Y/W .3R with o/p set to 8R Not returned in 4 months of use with passive venting mod, for fan retro-fitting, so presumably my venting mod was enough. From a USA user "I came across a thread on cooling issues with an Ashdown Peacemaker I bought a Peacemaker 40 in the US. I have experienced issues after a few hours of having the amp on. At one point I use to put a window fan behind the amp while we played! I thought about mounting a fan as well but I would prefer not to cut a hole in the outer cabinet if possible." Ashton GA80 guitar amp (Australia) RoHS date of introduction for Australia ? Anyway 1/4 inch i/p socket too weak even for domestic use , breaking up in a few years ( within RoHS regime), no obvious datecodes except main electros seem to be 2000, otherwise maybe 2004 or 2005 IC dates. No-name flimsey junk , the type with 2 insulated change over contacts. On trying to work out the functions, apart from the tip contact/grounding setup there is a line to one of the isolated switches that grounds at plug inserted and o/c when removed , it goes DC connected to the base of a pnp SM1015 transitor - function ? If it kills the gain for bang-less plug insertion then it would only work for insertion , not removal, as that switch makes before tip makes/breaks ground Luckily the owner wanted a reliable input socket and was unconcerned about the loss of the plug-in de-thump cct. To replace the domestic headphone socket (has isolated switching) would have been a work up as 0 or 15V on that control line so could not use an effects pedal type ring switch action. And the ring switch for a normal stereo 1/4 inch jack is the wrong action for here anyway, requiring an inverter somewhere or one of those awkward and rare offset 1/4 inch switch actions. cct proper, holds off full gain for 0.5 seconds or so after plug insertion, all the while removed 30dB or more gain drop via 15/-15V control into the first amp. Although no obvious PbF solder problems the original input socket had thin+wide blade pins going into holes of that wide diameter and loads of filler solder, asking for problems with ordinary solder let alone new-fangled More as a reminder to myself, for the next time this problem appears. A work around without having to cut into the existing cct to put in an inverter. Use a small SPDT relay (+emf diode) with power adapted from whatever convenient rail. Permanent ground on the flexing ring contact in a 1/4 inch TRS socket and the fixed ring- contact to the low side of the relay. The added delay, due to relay action, only adding to the desired effect of delaying the removal of the gain suppression until after tip contact is made ( unless someone is very slow at plug-in) Uses 2SA1941 ,2SC5198 2K7,10,100,2x .22 A1837,C4793 7815 , 7915 ? not seen 220R for phones 34-0-34V ac 19-0-16V ac That SM1015 base goes from 14V to 14.6V in each state and Col 14.7V to -14.8V springline 27R,215R Audition spring-line amp Excessive white noise. Germanium technology low power practise amp one time sold at Woolworths with detacheable 15W speaker.Replace the input side transistor 2SB440. Backline 600 Seems to be a notorious problem with fan system on these, so many I cannot find a recognised solution in amongst the complaints. Monitoring V to the 12V fan takes ages getting from 1.2V to 3V and stops there as fan starts taking current at 3V. Already the h/s is too hot too keep fingers on. I never liked the idea of slowly ramped V to fans but will ask the owner if they want the temp monitoring changed or fan on all the time. I'm reluctant to bend thermal sw back to reveal the other face as pins look semi rigid and probably not marked anyway. Not so straightforward a work around. Mark the 3 screws with nylon spacers before dismantling h/s TO126 C3205, Q15 TOP66 C5242 Q24, TO220 A1837 , Q14 12,.1R.68R 8R cold over R64 at mains 1R over R63 .9&.5 "diode" over Q24,25,26 1.6&/5V "diode" over Q21.22.23 s1 th sw NK 1.1 with Q25&Q26 JM65RC TO220 Q27, A1837 Q28 Active monitoring with a TO220 device LM35DT, linear output, and perhaps JM65RC means selected for 65 deg C. Plenty of data on them but will have to sketch out the LM35 and 2 transistors to see a way around dropping 65 to 40 deg C in effect The self-tap screws supposedly holding the IEC socket to the chassis have no bite and so each insertion/pulling of the line cord plug, stresses the PbF solder joints on the pcb carying mains voltage . Solder OK at the moment but looking a bit suspect already and so a year or two on ,a conflagration in the making. So remedial solder and bolts and captive nuts replacing the self-taps. The cut out sw is nearest the hottest part of the h/s so cuts out before the fan drive has really got going, it still has to cool down the bulk of the heatsink, all the while the underside is still going up. I can see a diode going in "under" the LM35 to raise the 0V output for 0 deg C to a voltage that will at least turn on the pass transistor to the fan, at room temperature, and then increase it with use. As it is the heatsink gets too hot to keep fingers on (50 deg C?) before the fan gets any voltage at all , surprisingly 24V but 3V will start to turn it. A great advantage with always-on is that the user knows the fan is in working order right from the off. I tested the cut out sw in situ. I can just make out markings through the insulation wrap. 028 A 20 161 perhaps 161 deg F Sw goes o/c about 80 deg C and s/c again 65 deg C marked 028 A 20 161 Don't try this amp with no heatsink attached as the quiescent current is too high without heatsinking the o/p devices If the amp is left switched on with no input the quiescent current is enough to slightly raise the h/s temp to about 30 deg C and fan comes on now I suspect the problem is drift over time of the Vbe of the drive transistor, change of 0.01V there leads to change of 1.5V on the fan , so if Vbe rises a few mV the fan will only come on at 50 or 60 deg C, too late to be safe. 3x "17 deg C "/ 0.17V of lift from 3 SM shottke diodes under the sensor is about right to get the fan turning properly at ambient 15 deg C or more. .27V over shottkys (.44V at DVM measurement) and .25V from sensor gives about 5V on fan .17V one shottky not enough .29V Ge gives 1.24V .55V Si diode is too much Definitely a PbF solder amp from 2007. Made in China for USA for export to the UK but presumably the same for domestic USA use , no mention of PbF on pcb or rear of casing Tr 12.8R//.6R 10R, 5W +/-60V umbilical 14,0,-14,-,2.1,.1 3.3R, 2x 10R "harwin" connectors have locking pips on the long face end cheeks 33R from +60V rail Vs from R41 near umbilical Fan stabilised with o/p of .57V [.3 (ie 30gegC)+.27] and fan having 7.7V, room temp 21 deg C Load test 400Hz , 5.8V ac over 4R 22.6V over fan .23V , .66V on combined sensor output Behringer maybe rebadged Alto eg Behringer MDX2200 composer Pro near enough same as Alto ACL2Pro Behringer LX1B-PRO , Bass V-amp ,2003 N11999 compliance Behringer SL2442FX PRO , mixer desk, 2004 This 24 ch mixer has been "repaired" twice for a very rare random fault. Recurs months after being "repaired". Loss of L channel output at the XLR. Previous person had obviously looked at the most likely suspect of the 1/4 in sockets for insert , with bypass contacts and XLRs thmselves. Remove graphic panel buttons before removing main pcb Both Main/Sub push-push switches, 4 pole C/O are very suspect in the FX sections, half a mm pushing when out will loose the effects component of L or R channel and a bit more, full loss of one or both channels. Any other suspects to check? I'm surprised the schema are out there but minus smps so some details taken, just in case. switcher driver ? (reverse of pcb not explored) maybe designated 04N68, TO220 , usual 0/O possibility (obstructed viewing) other marking maybe 1M360 googling around turned up "Incidentally, on more than one occasion I have repaired a Behringer with this exact same symptom (no L ch), and it turned out that one of the main bus tracks runs right at the far right edge of the PCB from fader to output jack socket section. When the PCB was installed into the chassis, something sharp caught on the PCB and partially cut through the track, which eventually failed some time later." Got into that panel now Although no observable damage to that trace, I may as well run a line // to this trace while in there. Looks like that mod, replace the 2 4p c/o sw , the 2 1/4 in sockets for Insert and at least remove the main slider , probably replace. Putting some alternate sets to the pins of the interboard headers, and keep fingers crossed. After that, should it bounce, I suppose its a matter of building an active buffer and LEDs as telltales , half way through the outer stages, to localise down a bit. I will try and advise the owner to swap to using the upper channels , in case its a problem earlier on. Force on the 0.25 socket L insert sw about 700gm, to break contact, about 1400 gm on the R to break contact is a bit suspicious. Normally I would expect problems in the order of 300 or 400 gram contact force. Found a pair of 4w c/o switches to fit in the 13.5mm of clearance space. To desolder the no-name black 8x8x12 mm 4p c/o switches you need to sling .6mm wire under the sw body and pulling when desoldering. Normal clamp force over the body is enough to break-up the casing of these very weak switches. At least I could see inside and no wonder they're problematic. Remove 2 side cheeks and 1 sc each side under Leave 2 ps sc in place in square recess and remove 2 sc at the IEC, open and disconnect ps from pcb. Excessive hotmelt glue on cons , pick off with a dart point before breaking. Remove the ps to make more bench-friendly. Bend the 2 prongs to release phantom sw lead. ps 180uF, 400V, bowing top 270R, R27, 470K 2x22, 2x100 BYW29-200 CNY17-3 BD239C, 7805 T1 clip protruding so bent back so 270R can be pushed away from the NV cap, held to the clip using a loop of silicone sleeving Master slider 10KD , 1/2 track 90% , log Removed both Insert 1/4 in so and pushed 14x10x1.5mm into behing bypass contact and glued in place. ps ribbon in phantom mode red 15,15,-15,-15,0,0,44V,5,.025 Replaced both 4p c/o with Secme doubled up miniature rotary sw. With wires to the pcb holes under the replacement sw , just about room with the 13.8mm of clearance between pcb and front panel (brass standoffs) Sub posistion is lower (end of front) when sw pushed in (as original) electret microphone is right next to the PTT sw Beware of misaligning the TRIM LED on edge of pcb Before fitting the main pcb back, make sure the shield for the digital board is fitted. No R op now, with test signal , signal at in and out of both L & R insert socket but not at top of MAIN slider or MON slider. Tape out L&R ok I'd fractured a trace at the insert soldering. Chirps and hash on phones output due to bad contact at large ribbon IDC connector. Replaced the IDC inside of the original with a plain unpolarised one and cut off the original, enough cable length Added a large cable clip bolted through the convenient hole in the pcb to clamp the centre of the 40 way fixed IDC at the othe rend on the op pcb. Check it clears the ps. Check all 40 ways are good. 4 chances each of L and R signals failing in passes through this ribbon. To replace the chassis back leave the 2 slotted sc at the ps loose fit until the IEC and sw are in place. Place a large cheek sc in each end for temporary alignment for the small sc Returned later , the above problem resolved but now loss of FX 1 function FX1 present on Aux Send 1 out. Select subgroups and FX1 signal there. If the memory push action stops working, remove the knob and screw up a bit of paper and push insid ethe knob - it was bottoming out against the panel. Main-L out of FX1 on 4w sw connects to Main-L of FX2 at its corresponding 4w sw Cross compare FX1 and FX2 / main / sub sw in all 4 combinations for a broken pcb trace or via. Not seen as left the pcb in place and 2 wire bridges used instead. 4 end poles of th emain/sub sw 4w sw, go to 4 track ends of the main Stereo pot. pins 1,4,5,6 with pins 2&3 to gnd IC53 Inverts INVERT line L &R Beware of the metal shields under the DSP pcb as it is floppy and could short components. Behringer UC200, chorus effect pedal Used with DC supply, not battery (horrible battery access). Only unprocessed sound on pushing pedal , but the LED comes on, usual brightness. I've not had any failure with it, normal function. Somewhere between 400R and 1K in series with the supply, simulating dirty contact, processing fails and LED on but only feint. So not power connector diverter switch or input Ring/Sleeve contact problem presumably. PbF problem, but where is most likely? Incidently is the casing really ABS? says so on the mold mark inside but it has the look and feel of nasty breakable polystyrene I was monitoring the B output and that was ok, assuming the A output was just feedthrough , but RTFM fashion A and B are stereo outputs and he'd been using the A output which is failing to switch over to chorus , so will have to probe the 4558 that feeds A, if not B I suspect I'm chasing scotch mist. Owner uses wiht guitar , then wants to record with a stereofied version. I suspect this is a different flavour of UC200 although no subscript found. I was noting upside down and A output is chorus and B is feedthrough. As both outputs of the chorus chip are bridged across with a pcb trace, then perhaps only ever a mono version. Press in pivots of top cover to release cover to get to battery V3207D delay line,V3102D clock, TL064c. Input is not isolated switching B o/p at p1 of IC3 p7/p8 chorus o/p as IC1 combined o/p p7 a=nd p8 so not stereo T6 control? for A T7 control? for B T1 carries chorus T9/T10 for power on/off chorus function is still on with blue LED off for noisless on/off Big Time practise amp failed mains fuse assembly uses D1406 and B1366 , 2x 0.5R, 4559 Blackstar Artisan 30, 2008,ROHS Blowing fuse 100K,100K,1k,1k,100K 1k,2k2,68r 10W 4x1K on EL84 20K between pairs of G1 40 percent mains fuse ok and HTs 127,135,133,135,137,137 about 60 percent and sound out EL84 -,0,3.8,0,0,-,high,-,176 HTs 155,159,162,170,176,177 100 percent mains, all electros with 8R load 2.6,126,1.4,270 270,1.4,278,1.4 1.4,302,11,318,320 all mid pots 10mV 400Hz in Hi, 3.1V over 8R Fuse holders in awkward position and messed up cap and bad contacts. To remove requires heating back nut to melt lacquer. Assumed intermitant making was blowing fuse although no reported noises. Boss BCB-60 effects pedal board Is there a problem with the 1/4 inch sockets on these? Especially the input one that must take a lot of guitar lead yanking. They are the flimsey domestic, no name, hifi type things and used vertically at floor level so any stage crud gets in them. Intermittant through-signal drop and I cannot induce collectively or individually and will have to check the internals of all 5 pedals plus daisy-chain leads etc. Although metal mounting bushes on these sockets, it discuises the fact that all behind is flimsey plastic. The one taking the in-use strain had its tip contact displaced outwards relative to the other one. Making contact, but presumably not reliably under temperature change/ grime etc. I replaced both with standard robust plastic bush sockets wired together and space made for them , being somewhat larger. And checked the internals of the 3 out of 5 otherwise suspected pedals, and leads. Looked inside the board output ones as well, because leads to them could have been tripped over at some point. footprint space 12x13x27mm, so small, a justification for use, logo something like HT curved to fit inside an absent semicircle and type numbers variously e/b/a/h/g. Sighting through the barrel the tip contact should be in line with the centreline (centre of ground contact) but the stressed one was 2 to 3mm off line. The rear plastic closure square will come away on releasing the pawl. Grotty PbF-looking soldering on the output interboard ribbon cables Both i/p sockets (as daisy chained so either could be used for lead in)replaced with manly ones. Another amp roday will have a manly 1/4 inch chassis mount socket replacing the pcb mount failed one. Boss OD3 uses M5218 Boss TR2 uses M5207L01, 3 M5218 Ibanez TS9 uses TA7555 Boss BR600, digital recorder, 2006 Q47 an 8pin SMD presumably a powerFET switch, with an erupted hole in it. Marking BB ??F1 probably ?? as 1 or 2 missing characters 3 connected pins of the IC go to batt -ve, single pin via R2 a fusible resistor of .3R to batt +ve (9V), and 4 pin combination on to the rest of the circuit via the on/off switch. Quite a bit of space to fit something bigger than the original, but what sort of rating or identity and then data for a BB??F1 top code SMD ? So far not found an 8pin BB powerfet identity further reading but no identity of the powerfet, www images swamped with external views of course and 1 out of focus pic of the diode fudge in the above thread The Service Manual identifies it as VEC2302 Dual p-ch 3A,30V, buried in the datasheet Marking: BB With the ex-SOIC off the board then traces are consistent with the pinout of that IC with both devices paralleled Both devices are in series: S1 -- D1/D2 -- D1/D2 -- S1 1 7 8 5 6 3 This is in parallel with the not fitted D2, so you can just fit a diode in position D2. Maybe a Shottky. D2 Anode ----------- D2 Cathode I was going to put an IRF9532 in there as plenty of space for a TO220 but I've no idea what the seriesing is all about so a couple of paralleled shottky SM diodes went in at D2 pads Owner lost the original plug in ps, and tried using another 9V one of the wrong polarity. I changed the connector and polarity and the unit worked for about 10 hours and then bounced back. So something to do with reverse polarity stressing or knocking out one powerFET initially but continued for those 10 hours with the other one or something like that It does not say regulated but I had checked it initially and it was 9.6V,no load, and as rated .5A then probably good enough. Original Boss one not known Talking to an engineer familiar with solar PV controls. He was reminded of the anti-shadowing bypass "diodes" in solar panels. Otherwise a shadow over as little as one cell will kill the output of the whole array, so as little as a good dollop of seagull shit is all that is required. Say 50 cell panels and each sector of 5 can be bypassed by one of these 2pin powerFET devices built into each panel , output falls in a sector below a trigger level and "diode" kicks in bypassing the 3amps or so of the rest of the array but only dropping .05 volt, so overall array efficiency drop of 1% instead of 90% or whatever with the shadow of a chimney or telephone pole or whatever. PS pin is negative With no lead then battery wiring is connected to the power in socket. Previous leaking of a battery leading to corrossion of battery terminals and no battery ]operation, when working Green fuse is Tyco 7X7 marking 7 overlaid pair of Vs inverted 7 , resettable .7 amp Boss CS3 Boss ACA adaptor must be 15V or more using 9V supply is too low. 7V dc on battery is too low Changed the 220R 1/8W on ps line to 35R cold ptc thermistor and 10V zener Boss DD3 digital delay foot pedal, version 3B , 2003 ? Does not always latch on, momentary footswitch seems ok eg physical switchpoint, zero ohms on , the latching is via RC and taking an input to a 74HC00 low. Mark all the 1/4 sockets before removing as their orientations are critical. Original problem was probably (from sooting/tiny etch mark) the electro (too long lead had touched the adjascent ground line so cut it back)at the 5V line of the SM 5V regulator marked "A E" , IC9 I don't like the indirect footswitch ground line via 2x 1/4 inch sockets and casing but nothing loose. placing various Cs across the sw made no improvemnt. Desolder the small pcb off the switch so the metal casing can be removed for ease of working on after demounting the sockets and pot board. Did a subcircuit determination Using one wasted, as paired-up, input to one of the SM 74HC00 gates , cutting just one pcb trace and added an R,a C and a D constructed a 0.4s monostable, pulse stretcher so now latching properly. It does not seem to have affected the hold mode option either. Footswitch goes to ground to activate, with input lead connected. via 100 ohm to pin 1 of 74HC00, linked to 2 (H via 100K), 3 to 4, 4 to 12 and 13 and red lead to hold option on mode sw, 5 (H via 100K), 6 via 10K to pin 62 of main IC, 8 to pin 59 of main IC, 9 to brown lead and hold option on mode sw, 10 to 11. Soldered 1M between pin 2 and 14, cut trace between 1 and 2, then .47uF SM cap from 2 to diode to pin 6 to conduct when pin 6 is low. Latching failures seem quite common with DD2 and DD3 according to the archives. The line to the led had been squashed against the power-in socket. The input socket switch only functions with battery power Roland BOSS DD6 effects pedal ,2002,(no repair but did create a noise generator , see tips files) Dropped into warp mode of its own accord then failed to move out of bypass to any mode Originally thought the mode switch/pot was flakey because about 12K left at the end of the track, not knowing internal endstop, so beware. Thinking bad contact could make the mode selected be "0" , the warp setting. Mode selector switch on a Boss DD6 effects delay peadal. Looks just like the other 3 green case subminiature pots each marked B50K , by Alpha. Nothing external to indicate the 7 posistion "switch" is different. Inside a second properly molded-in internal endstop as well as the normal one, so track is limited to 3/5 of normal full track. So if wiper breaks, due to grease, then pedal has a mind of its own which mode it wants to be in. When cleaned out measures 0, 3k, 8.1k, 13.4,19k, 25k,30.6K in the 7 positions and over full track 48.6K. Pot used as a mode switch yes, with vague areas around the knob designating the mode but not ever seen a dedented pot before. And how are they assembled at manufacture.? Externally there is absolutely no different appearance between the "switch" ones and the pots, I've looked under an inspection lamp, no odd dot in the molding or any other difference. If you turn the shaft then it clicks into the dedents, being the only difference, but that is not visual. functioning as a switch, relying on high linearity and non-variation of resistance for firmware interpretation. There is a difference to the pots, they are ink stamp marked 2G on the side, this "switch" one is marked 2H7 Laid out on a clothes peg and mm rule. Third part is the track section inverted to show the second green endstop. The fourth image unclear in pic, as buried in the body, holds the dedent wiper. One detent that shows is to the right of the purple > and the endstop arm marked A testing the 9V line , ohmic, varying 150 to 250 ohm and drawing well over 55mA spec current. unidentified ps components Perhaps voltage regulator or bucky controllers BJSQ 5 pin , size of body area, 2.8 x 1.5mm, SOT235, IC9, Overheating ps components same physical type but top code JAPL 4 pin on perhaps a pass transistor, size of body 4.3x 2.4mm, IC6 JB1G (number one not I) and printed as 2 pairs , Q15 Replaced with sm BCW67CTA , to proceed. BJSQ replaced with a LM317 set for 3.6V as the datasheet for the AK4352 DAC said maximum ps was 4.6V but was driven up to 5V via Q15 and DAC and ADC seemed to run ok at tehat and probably suppoosed to. So don't know what BJSQ was , perhaps a supervisory IC. Back to some useability but still somewhat high consump[tion. Testing 9V line now , probably as it should be, Diode check 1.1V / 0.6V and on R like testing an elecrolytic. Test connector pins 1 gnd, 2 pin 19 of IC5, 3?,4?, 5 IC7 pin1, 6 2100 supply, 7 ? ucontroller responds to function changes correctly but audio output stays at bypass. That u sends data that varies on function change to pin 63 of a Boss proprietary 100 pin. AK5353VT ADC sends data to pin 68. There is data flow to the RAM but otherwise nothing comes out. The AK4352VT DAC is ready to receive but nothing there. This main Boss chip runs warmer than should and more than the 55mA consumption , in specs In this non-working state and deliberately feeding with 7.4V and not 9V, the 5218A supplies are 6.6V and the 2100 like the main chippery is 4.3V, probably should be topped out at 5V , regulated with full 9V Boss GT-6B multiple guitar effects pedal board, 2005 Two of these known to the owner of this one have shown the same symptoms, but never connected together in any way. The other one apparently corrected by a factory reset (coincidence?) At switch on the display continuously scrolls as though one of the up or down bank select pedals is active, ie looks like the action of someone continuously turning the rotary encoder switch. Have taken apart but not reassembled yet , unenclosed . Only 0.2mm differentiating first touch to click over of the very basic click switches under all the foot pedals. The "wah-wah" switch is different action. Is it a stock fault of deflecting steelwork/pivot wear/bending pcb/expanding soft inserts? causing engagement of these switches, then just washer packings to correct for a short time until the problem re-emerges) or something more electronic/software or internal rotary encoder problem Not a stuck sw problem. Unlikely rotary encoder sw problem as physically rotating it changes the 7-segment display but the auto scrolling error function does not. No susceptibility to touching components. Select a funtion like tuner and the display stops scrolling and gives tuner display. Disconnecting all ribbons except the display one , the scrolling display still there so a main board problem seemingly. I suppose ESR caps check is first port of call. User manual from Bossus site and schema etc on e-service I asked, at receipt, whether this one had been connected to a pc and it had not. I've just asked whether it had been connected to a sequencer and so maybe the other one had as well, transferring corrupted code. This 6B same as the e-service 6 pdf as far as display is concerned , buffers between uC and display seem to be operating correctly but still scrolling with the switch and rotary board disconnected. No obvious ESR problems, little much else to do, check a few V if 6 and 6B agree there. With all ribbons disconnected other than display one I noticed that the display stabilised if "digital" fingering of the empty mainboard socket for the ribbon that goes to the sw board and pair of analogue mx chips. Reconnecting that ribbon the display still scrolled but tugging on the fixed end of the ribbon stopped it. Resoldered the ends and display and overall functioning seems normal, eg up/down bank buttons function, unlike before. Nothing obviously wrong with solder or the crimp? terminals to the wires that are also the solder points but something wrong there. Not PbF but resoldered all 4 such ribbon fixed ends JIC. As maybe generic Boss problem area they are no-name white "Harwin" 0.1 inch type connector system for discrete wire ribbons, same crimp? system at the fixed end (inserted into the housing then soldered to pcb) and socket end , so standard sockets at one end and solderable thru-housing and pcb pins at the other. So is it coincidence the other one was playing up the same way and was genuinly cured by factory reset or same wiring problem coincidently disappeared for the present on that one? Or of course some other intermittant problem with this one coincident to fiddling with one connector, the repairman's dilemma. Repairing (or not) by divination in effect. I've now had word back that both units have only been connected analogue to amps and guitars, no midi or digital connections. Not bought from same supplier either. LCD ribbon, line 6 disconnected, top line of pixels only on,ditto line 4 and 5 2x4051 ribbon and display connector then no scrolling. Remove 2x4051 line and scrolling returns. Same scrolling with all othe rribbons connected, but not the 2x4051. Before dismantling the wah-wah, if necessary, monitor the pedal force to return it as found. Boss ME50 multi effects pedal All LED flash on &off then latches up with the seven segment display showing the decimal point only. Removed the single board from chassis No stuck sw, no bad solder joints seen, no bad ESR caps. One time only, pressing on area of pins 1 to 20 of 144 pin Boss chip the board started responding to switch pushes, not repeatable since. It will read data from the EEPROM always, so can read version number and also can do factory reset. Sometimes it will function, responding to switch pushes, from switch on. At least a full service manual with all data lines etc is on e-S. All datalines between DRAM and uC have continuity, in area where there sems to be pressure sensitiviyt. Now to power up and check some DCs Leave 3 pedals in place and remove 6 rear screws to remove pcb Annoying rattle on moving is nylon rings over the LEDs Reset IC M51957B6P topmark 957B 10uF across existing 1uF and delays reset by 3 sec from .3s 67.7MHz just observable on 20M scope expression pedal .1V to 2.7V range , 3.3V 8.9V in 7.3V at IC9 7.3V at IC1 supply 3.3V on all pots dot in 7 seg display means manual mode but no further response IC3 codec p10 22uS pulses p12 2.5MHz , p11 11MHz IC11, p16 active when responding to sw and any pot turning , never activity on DRAM Decided part of digital signal processor chip faulty Boss ODB-3 bass overdrive Sometimes fails to work or stops on battery and sometimes on adaptor. The plating on the power socket metal parts was breaking up , presumably interfering with the switch contact as well. Boss PSC 2036 broken and lost UK dummy pin 9V 1A smps 3mm a/f recessed screw under the label. Could not find 3mm spinner so ground slot into the head (and plastic) Now know what PPO (Polyphenylene oxide) smells of when burnt a pungent tarry phenolic smell. Maybe swap the housing next time . Robbed a pin off a scrap wall wart and cut a fare face to mount to casing. Opened out a guide hole in the hollow centre of the pin to take a screw and also superglued in place . 400V 33uF, ER401 diode , 1A fuse, NEC 2561 opto, TO220 TOP223YN, zener ?150? (obscured, 105 deg caps 470uF 10V, 100uF 15V Bullet VM30 combo, GDR from 1990 But looks more 1970s . Pull+slide the covers off the handle to release and springline ICs marked "X2 080" ,"X8 761" ,"TL 761" (not opto) ,"X8 082" ,"X6 081" ,"X6 082" , V4007D B080D = TL080 B081D = TL081 B082D = TL082 B761D = TAA761 V4007D = CD4007UBE the X* numbers are datecodes 2x KD607 80V, 10A, SD339 and complement SD34? SD335 , 336 on preamp , 2x330R , 120R An E-line size or varicap type package of a diode like SAY32 marked 32 VV or 32 YV, 32 volt zener ? The ones marked 15 are the zeners for setting the +/- preamp rails. Works for 1 second and then fades out. There was a burnt section of the ground track between the secondary ps side of the preamp and the signal side. The grounds of the 1/4 inch sockets were measuring 6V. Bridged temporary with 68 ohm and measured .6V so bridged with a fuse holder and 1.6 amp Probably due to operator "error" and have replaced with a fuse there. Fusing current of approx .16x.8mm copper strip about 7 amp Eventually in use this fuse failed gently, so replaced with a 2.5 amp antisurge The siting of the ones marked 32 maybe for overvoltage sensing , but not normally in service. Probably those are 32V zener. There are 2 more of that package on the preamp. These labelled 15 X4 and next to the +/- pass transistors for the preamp +/- rails so probably 15 Volt. Springline 315R and 10R, if the 10R one is disconnected there is distortion to the output with reverb set to zero. Repaired now, but for the archives there is a safety issue with these amps. The earth bond wire to the amp chassis is fine but the bond to the front panel metal is very poor, just a brass rivet to the phenolic of the pcb, of a few ohms drop over the years. Needs redoing to the metalwork properly. Top handle screwed into the reverb tank so leave in place. Lost rear bolt anchor. Hot melt glued in place a captive nut Burns Orbit Three , 1967, ser no 40* loss of ch 1 and ch2 over the years , broken handle someone had disabled Tremolo and Reverb at some point ant too much missing to easily rebuild 14 Ge transistors and 2 zeners o/p Tx KB1923 2/2/4R across the top between the 2 paxolin tag boards not along the boards TR3 near TR8 NKT404 TR15,TR14, missing?, TR13 TR17 (near intensity pot) , TR16 Black scale rings under the knobs are glued to the facia , heat with hot air to remove and to replace (removal required to undo pot nuts) Bad vol pots leading to loss of ch Someone had replaced TR4 with Si NS BC1547351 ()BC154 of 1973 ? ) 3 x Jensen C10R sp, 2 measured 11.9R and 1 11.4R Handle repair Original core was 7mm sash window cord , sissal so broke of course. Clad in sewn thin leather which had failed as well . Main handle thick leather with figure-of-8 x-section. Pulled and pushed out the glued core and thin leather from the main handle to reuse the thick leather part. 5mm polyester guy cord , 4 turns threaded singley with stout wire through each side of the handle, through the cab fixings and also 2 pieces of heatshrink. Heatshring large enough to take the 4x polyseter and small enough to slide in plain run of the handle, the othe rrun is lapped to sew-up. Tie off the ends with an extended "knot" and push into the overlapped run of the handle so wedged tight but next time may add some hotmelt string for the heating stage. Balance up the 4 turns of cord. Encourage the heatshrink out of the other run , through and around the fixtures and return into the other handle run. Centrally posistion the handle. With something wedged under the handle, heat the heatshrink with hot air Carlsbro, late amps, linked with Laney so check via google images for similar kit the schemas. Carlsbro BassBeaver, 20Kg Broken pin on input socket, desoldered but soldered wire to the remnant and soldered to the nearest component down-trace. While in there noticed a burnt 2W resistor that was o/c. This was a snubber at the speaker output consisting of 1uF,100V non-polarised electrolytic and this resistor. Remaking the remnants of the R it was about 3.9 ohm. Nothing on TDA7293 product pdf. Replaced with a 2.5W, 8.2 ohm with long solder joints along traces. As probably o/c for months obviously not too critical The R-C combination is a Zobel network "can be quite important to the correct operation of the amp. It's purpose is to neutralise the inductance of the speaker voice coil, with the intention of flattening its impedance curve at the HF end. However, without this network in place and doing its job, I have known output stages to burst into spontaneous ultrasonic or even RF oscillation. The values of R and C are calculated according to some esoteric formula that I'm sure real audio buffs could quote at you chapter and verse, but the general rule of thumb is that you start with a resistor of equivalent value to the voice coil's nominal impedance, and then calculate C from there. " - Arfa Daily also +-41V, uses TL071, 072 Resistors 150 ohm, 2x680 and the unknown 2W Carlsbro BassBeaver, 2002 Zobel 4.7R 2.2uF 50V unpolarised 150R, 2x 680R, C547, BC546B Gain pot is set back so needs a starwasher and the grounding loop. Carlsbro PA100 Dropped then nothing ok on receipt but bad rear send bypass so replaced the socket, cut the solid wires to release,and rewire in 2+1, 2 to stubs and 1 to pcb Carlsro Cobra PA100. 1992? Cuts out due to send return bypass sw Tx 23.2R/1.8R Tank 27R/197R No op but pa works inserting signal +/-15V on all 072 With test signal at input and xtal earpiece then signal on send so moving contact but not the static one. Replaced 1 thin and 1 thick bush washer on each control Carlsbro Cobra PA100 Blowing mains fuse . Under test the LED would noticeably dim if insulated 600R mic in low Z input in one hand and other hand brough near to speaker will introduce 50 KHz oscillation and excess main current draw. 50nF across PA input dropped o/p 50 percent at 10KHz , perhaps 30nF next time. A lot less prone to oscillate. Carlsbro Cobra , 1986, 28Kg Someone threw something at this speaker in a Carlsbro Cobra combo. It works with distortion, like a weakened form of one of a pair of complimentary drivers working only. By digital probing (using my fingers) at about 4 o'clock position , unpowered, the rubbing resistance feel to movement of the cone disappears. Same if powered up, no distortion, to a power level where the effect of my fingers damping comes into play. A liquid that will contract on drying to paint radial stripe on cone and dry and test, repeated until problem goes plus one or two more stripes.? Or would freeing the rim or part of the rim of the cone by hot-air heationg and reseating all or part be better. If part then release 2 to 6 o'clock say and pull or 8 to 12 o'clock and push, my guess is pull would be better. The central dome was buckled in so attacked this first. Drilling a few 1mm holes and using a dental sickle brobe managed to pull it back into reasonable shape. Somehow that corrected things, just a small puncture in the cone periphery to patch over now. Uses 2x 3055, 2x1C03, 1C04, 2x 10R, 2x 0.24 , 150 ohm on phones line in the pa. 1C04 misread as IC04 TL071 s , 2x680R , RC4136 on pre-amps +-44V dropped to +-15V Someone had been in there before and managed to disable the reverb. The transmit side of the springline wire has no earth return, just a dummy pad on the pcb. That person had soldered the braid of that wire connected to the receive ground to the driver output. Tracing the RC4136 quad the spring line driver output is pin 3 o/pA via 100 ohm to springline and 220p+100K return to "A" i/p and via 100 ohm to i/p(D). Receive side of springline connected to pin 9 i/p(C). Carlsbro Eclipse 12, 1998, 12 ch mixer amp Drummer laid his snare drum brushes by the side of the amp and the wires flicked into the vent slots on the side and killed the amp except for front panel lamps. Replaced 2SA1668 pre driver, and FS7 fuse and added "crockery scourer" grill cloth inside the vents either side. Also for personal H&S cut off all the jagged corners on the sheet metal work with double action snips. pa uses MJ15024 / MJ15025, 2x 2SC4382, 2x 2SA1668 , 2x 4580, TL071, BA10393 , 4093 IC03, 7815,7915 digital board TIP132, 7805, 7815 discoloured 220R ?, measured 265R over each in cct. Disassembly, remove side panels, remove top and then divider panel 5.7V, -15, 15, 15/5/50V, 47R in cct, 2x 10R PL4 for LCD display panel PA works with all mixer panel disconnected PL7 2,2,2,2,2,2,7,7V PL3 0,15,13,13,2.1,0 PL4 6.5,6.5,6.5,6.5,1V PL8 2.2,2.2,2.2,7.2,7.2,7.2,2.2,2.2 PL1 -12.8,2.5,17.5,26 HT 68,0 main bridge rect ac 102V, 138V dc othe rbridge 18.8V ac Carlsbro Equinox 8150DSP, 2003 Music stand fell on to the sliders area and snapped off the stems 4 sc to separate amp and mixer break nail varnish before removing ribbon cheeks , 2 pk under, 3 m/s sides knob colours G,3xR,2xB,W ,then R/B/B top panel 9xpk I/O area and 11x m/s 4x star washers on the top 4 so only Slider logos YD in a circle, A503 according to the user manual , ALPS probably rotary pots only. Tried gluing back the stems but failed removing knobs test. Headphone L is stereo Could not find stereo pots with same physical footprint etc , as usual. Robbed the sliders from a couple of pots with near enough the right size sliders. But the required tracks are L,W,W,R (W=wiper) wheras all the ones I had were L,W,R,W. Melted the plastic swaged "rivet" to remove one contact strip and mounted it back the other way and remelted with some added hotmelt. Although this worked the physical height was less and the leading edge of the wiper would touch a pcb rivet , 10% from 0 and 100% ends of slideway as the whole wiper tipped in moving. Cut some 1mm thick PTFE strips to lay under the slideway , ove rthe stem to pack out to stop the tipping and also ground down the rivets a bit on the touching edge to give an incline. Carlsbro GRX7, 1996 no o/p Smashed vol pot B10K, broken inside Red tank conn, nearesr Cab edge 7815,7915,VR on master panel Carlsbro GRX7, 1996 Sometimes failed to work and sometimes dropped in power and crackles. All the 1/4 inch sockets needed attention, front and rear. The signal pa/preamp interconnect lead needed attention The subsidiary +rail 156R dropper needed replacing. Uses 4x MJ15024, 2x SM2177A, 2x SM2178A, CBC182A, BC212 1C03 , 2x TL071 156R, 5x R33, 10R,2x 4R7 Mains primary 6.9 ohms uses +/-15V regulators on preamp Carlsbro Hornet 45 lead, 1984, 17Kg Distortion. Problems with output transistor, poor joint at base for some odd reason, heatsink hold-down bolts not tight enough. Soldering generally did not look very good - flux residue problem? - re-did all power handling ones. Uses BDW93C, BDW94C, RCA IC02, RCA 1436 Rs one measured in circuit as 156 and 2 not larger than 0.3ohm. Put a union in the speaker cable for ease of repair. 2 pairs of side screws at rear release the rear panel and front ones for front panel release, springgline fixed to centre board. Unusually the amp separates into 2 sections separately connected to the wooden casing and so electrically isolated as far as any earthing. The mains transformer is on the rear panel which has a proper earthing point from the IEC mains inlet. Power supply is plus and minus rails but the common is not connected to ground at all. The power and signal lead to/from the pre-amp / reverb is 4 lines : plus , minus , common , line level signal with no earth connection. The front panel is connected to the common , not to earth anywhere. There is much more noise immunity from general stray pick-up if I run a wire from the earthed back plate to the front so bridging common and ground but left as is. Interestingly this unit was yearly PAT tested and passing presumably earth bond and insulation test each time. If they had checked insulation resistance relative to the front panel , he assuming it was earthed, then could that have caused damage.? Carlsbro Keyboard 150 , 15 inch combo from 1985 TO220 devices marked 40871 and 40872 and also SM are presumable RCA40871 /2 , anyone happen to know what the TO3 devices are , presumably NPN , cold test seem ok. Usual Carlsbro, locked behind rivetted heatsink, otherwise prea looks like HH Marlin type amps I should know the identity of the TO3 tomorrow , both NPN on rechecking. Loose Collector bolts so I have to get to the other side to tighten. Not rivets , looked superficially like aluminium rivets . On Googling ,maybe cct similar to this admirable effort at unravelling to a schematic, the Stingray amp Even more like the Stingray. 2x MJ802 , 1 BC182 and 3xBC557 instead of 3x bc212, 100R between B-E of MJ802. Soft blown (not blackened) ps fuses and mains fuse , then abandoned for 10 years, no recollection of original failure scenario and nothing found, cold so far , a likely culprit Tx 8.7//.7R Prea ps droppers 2x 680R PA 2x.1 approx, 10R, 150R Don't remove the TO3 -C bolts as not captive. To remove PA pcb Remove 1/4 in so nuts, bridge rect bolt (heat solder points and push down the pins to relieve any stress in the pins of the bridge rectifier, regular failure point here) , undo the 2x h/s, and undo the B-E terminal blocks . As loose screws here and one collector nut probably the original soft blown fuse problem. Refix with laquer. The blocks need holding back or they swivel , on tightening the terminal screws ch1gain pot and main pot needed attention, usual Carlsbro problem of excessive grease inside the pots , getting on the tracks, not wear. No reverb function due to excessive Al corrosion on the tank sockets, leading also to a large amount of hiss in the o/p Prize off the spire nuts to release the tank and replace with normal nuts and a dab of nail varnish. Accutronics 4BB3A1B 24R i/p red side, 207R o/p black side Touching tank o/p pin induced amp noise. mid controls and 50mV 400Hz in and 4V on the tank input line without tank connected. Cleaned off all corrossion . Carlsbro Marlin 6-150 m2 1987 Insurance write off -not working after being in a room with a serious fire not associated with this amp. Some minor radiant heat damage and smoke stained but failure probably generally relevant to other equipment in similar circumstances. Although there are no ventillation holes with these amps there was considerable smoke deposit on the inside of the amp. The concentration of smoke must have been so great it had penetrated through the 1/4 inch jack socket holes. All these sockets needed cleaning but the real reason for not working was smoke entering the mains switch and IEC integral fuse holder and insulating the electrical contacts. Power devices 2 off MJ802 ok . To gain access remove one case end face,slide out top and bottom pannels after marking and disconnecting springlines. Remove the rear heatsinks to get to the power TRs that unusually B and E fix into screw terminal blocks on the pcb. Carlsbo Marlin 8400 Run for 3 days powering 2R speakers, saved by 5m long speaker leads probably. But not be break in the mains cable. So if repeated breaking carrying mains current , depite X class cap over the mains switch , would that be a more likely reason for the failure. ? Back EMF going well into the KV, punching through the insulation in the primary section. Failed primary and exploded mains fuse. Tx data core 2.35Kg 54.2mm thick with plastic tape cover , and 108mm and 54.7mm diam with tape. 47V , 5A inner wire 335gm outer 350 gm, 1.45 mm diameter. Primary wire .95 mm , 3.5V, .1A, CCD ac supply 10 turns .3mm Carlsbro Marlin 8400 , 2002 exploded mains fuse after running the amp on 2 ohm speaker load Tx primary measured 150R, variac at 20 percent jumps to high current. Tx blown , probably bifilar wound, certainly chinese made. Carlsbro Marlin 8400 , 2003, 400W mixer amp that immolated itself. Remove the front panel first to work out which screws on the back to remove. Q319 is a high voltage TO92 ( totally burnt and erupted but 2 isolated lighter blobs on the remnant of TO92 face are in the position of the isolated printed 2N of other 2N5551s on the board) then the melted blob component goes from the base of this feedback transistor to the speaker output line via the relay and choke. But it was 2N5401, (from the obtained schematic) which did not have a match elesewhere. The board is also burnt so overlay for this blob also missing. Anyone ever come across a metal oxide resistor melted to a 3mm diameter blob like a small tantalum. Metallic grey blob that measures 40 to 150 ohm or so across diameters, was 1/3W reistor of 330 ohm. The thermal heatsink monitor tranny was also exploded but as the face was gooed to the heatsink, that face was spared from charring/shattering and that was 2N5551 also, the thermal switch is 105 deg C. The subframe inside the chipboard casing is held to the chipboard with 12 x 4mm bolts, into clinch nuts on the outside covered with the black vinyl. 2 had dropped out and because you carry this kit vertically but use horizontally, plenty of chances for 1 inch long steel screws to roll into the power amp. But only plain washers and not star or spring washers under the heads and no varnish /glue spots over the heads to stop any undoing. On reassembly all internal bolts were replaced with star washers and glue spots. Audience were treated to piles of smoke erupting from the back of the amp - Hendrix was more impressive. Plenty of other damage but identifiable components for the others. 3 .5R, as well as above items and even a 5mm wide , current reinforced with solder, track had burnt. Copper trace 3.5 x .02mm and as 2 half approximated elipses of solder then area of 1 elipse of tin+lead which is Pi x a x b , a and b minor and major axes of .15mm and .8mm. Copper fusing current of the trace = 12 amps Lead+Tin elipse then 6 amps (not as much as I would have intuitively thought) Total 18 amps so 18/4 = 4.5 amps conventional fuse rating. Presumably the circular to sheet allowance would up this 4.5 amp figure , but by how much ? What sort of correction factor for thin sheet/non-circular heating then rupture allowance? I had a play with track width calculator and assuming it is still sort of valid at very high temps. Putting the melting point of copper of 1080 deg C then for 3.5mm strip of presumably 1 oz copper then the rupture current would be about 48 amps which seems reasonable. I knew it must be higher than 12 amps as that calculation was for round wire. By 1080 deg C we can forget about the solder run beefings. I think, assuming they survive ordinary power-ups a few times, I'll settle on a mains side 4 amp anti-surge , with a 5 amp A/S ready to hand spare and 2 off 10 amp quick-blow in the DC lines. Oriental script on the mains transformer and on a schematic. Q319 was 2N5401 and the R was 330 ohm. I'd not thought about it but VxV/R heating with single rail of amp voltages of 65V to melt a 1/3W resistor, not charr or explode it, it must be about 300 ohms or 10 watts dissipation. Uses 47V-0-47V ac, 3x 2SC5200, 3x 2SA1943 2SA1306, 2SC3298,2x TIP41C, TIP42C 2K, 6x .5,5W 2x 47 Replaced output trannies with lower voltage, higher current but much cheaper TIP35C and 36C and 2SA1668 to 2SA968 and 2SC4382 for 2SC4159 On bench tried powering with half rails of +/-30V , too low for relay to click over and no load at all. TOP66 of shorter form than the originals so ground split some standard spring to heatsink retainers and ground a small notch in the end to engage with the mounting screw plus star washer and glue dab and sprung against the tranny body (with glue dabs) so using existing mounting holes. With these lower rails .3, 30, -.14 and .8, 30, .3 on "positive side" TO220 and TOP66 .8,30,-.3 on thermal feedback TO92 and .13,-30,-.07 and -.4, -30, .13 on "negative side" Full rail voltages not measured. +/-15 V on the separate TO220s With amp outside cab but in normal vertical position and 7V ac of 400Hz driven into 4 ohms then temperature of thermometer clipped to the top of the big heatsink stabilised to 27 degrees over ambient in 35 minutes. No need to remove all knobs etc to acces the preamp control section of pcb. The master volume slider pot "knob" was broken , owner used a match. Plenty of sideways room to keel the slider over to glua an extension to the side. A bit of black cable tie bent and glued to double up in a vice. A bit of a bend in this piece to roughly match the leaning pot. Desolder the 2 pins on one side to lean over and introduce back into the cover and resolder after positioning better. Carlsbro Marlin 6 150 IV, 1995 ? ps +/-44V prea 2x 1K pa 2x 0.3R (in circuit) 2x 10R,150R TO3 nearest signal IP line probably NPN Beware the effects switch at the rear can give this "fault" as well if falsely engaged. All pots "worn" to the extent that its harcdly possible to find a position on any of them to pass a signal to the amplifier , so effectively dead when the main vol control becomes extremely "worn" as probability of blindly finding 2 active spots in a pair of controls with 90 percent defective is unlikely and pretty useless if found anyway. This occured at a period of cold weather which may be contributory. The pots were not worn as such. Believed to be the original lubricant had hardened over the active pot surfaces. Renovated all 8 gain pots and treated the bass & treble pots with meths bathing , both as per tips files. Tx 9.7R//0.4R,0.4R Carlsbro Marlin 6-300 Mk 2 1986 Blowing fuses. TR7 TIP41C s/c all round,R (R21 ?)between C10 and VR1 burned but probably 1K,R29 burnt replaced with 100R, other damaged Rs R9 22K ?, R13 3.9K ? R14 1K ?,22K ? preset burnt out. 3 of the 4 2N3773 defunct. As an interim replaced power devices with 4 x 2N3055 while checking out biasing section before replacing with 2N3773s. This amp had been repaired at least once before so cannot be sure if correct components or voltages but from repaired amp :- Thermo feedback used a BC182B, unknown CBC640 small BC182 type body in 60V section of circuitry. Other devices RC4136N and TL072 . Driving 8 ohm load DC voltages reading from heat sink side on track side of board. 4 2N3773 0,61.5,.4;0,61.5,.4;-61.2,0,-60.9;-61.2,0,-60.9 then row of TIP41C,42C,42C,41C .4,61,.9,60.9;59.7,.9,60.2;0,-60.6,-.5;-60.6,-.4,-60.1 Carlsbro Marlin 10400 , broken effects code switch, glued stem to basic plastic PCB mount hex codeswitch which only a marginal knock/heavyhandedness will break and of course fails inside the sw so cannot change with a small screwdriver as no purchase left. Electronics similar to Laney CD850S. leave 4x large screws on front panel . Remove 2x3 on sides and 4 large under, inner case slides out. "Digital" 7 segment number on overlay 200935 , not 2009 Remove 3 sides cover before breaking laquer and 2 x screened leads. Mark all leads before removing including spades behind mains panel switch pin8 of digital board binary1 then 4,2,8 and C is pin 24. See tips for beefed up codeswitch details. Check with owner what number on the front was the setting and check the 8,4,2,1 switches as unlikely to agree numbering. Carlsbro PM10 o/c powertone speaker , ITF, 6.4R replaced with Eminence Alpha 10 uses TL071 mains tx 21R, 1.8R Carlsbro PM12,1998 6sc around main section disconnect umbilical and both speakers, blue to main panel discon prea gnd remove 4 front grill sc to pull out prea 3x RC4136N. Tx 10.3// .9R 2x MJ802, 10R, 2x 1R 5W, 2x 10R 2W, .24R 2x 1C03, 1C04 piezo horn and 5.3R speaker Carlsbro pm12, 1998 Hum and vibration crackling and sometimes , PPI LED sometimes . Speaker cons loose also Feed XLR panel into cab, release front grille and end PS/PA panel to reassemble outside cab. loose gnd points, bad 1/4 in i/p so. Bad solder to Zobel L, and D3, and bad PA-PRE cable socket. Y is 0V line R31 2.2R o/c but not discoloured so fusible R and someone perhaps connected something they shouldn't Loss of frame gnd continuity as loose pot on the front Carlsbro PM15, 2001 Dual purpose 200W PA head or a foldback monitor. Reported occasional loud bangs and pops without any signal input, otherwise no distortion. Of course I powered up and with any amount of banging of cabinet no induced problem. Took apart ( need to remove the 15 inch speaker first ) and powered up with twizzle stick and serious bangs and whistles can be induced by tapping in area of electrolytics C1 (4.7uF,63V )and C3 (47uF,63V) and 2 small signal MPSA92 all at input from pre-amp. C1 probably AC coupling from pre-amp and C3 local DC rail decoupler. Otherwise no dodgy looking fuses, spade terminals hotspots or suspected dry joints anywhere. Replaced the caps and resoldered the trannies, removed Cs seemed ok and one trannie pin/solder did not sweat properly , contaminant ? TR3, SM2178A voltages, -59,-0.6,-59.8. 2 possible dry joints on this TR3 so added insulated heatsink tied to the pcb with cable ties. 45V ac on both fuses 60V,-60V on bridge rectifier uses TO3 devices BUZ906D & BUZ901D power to preamp 15.6V,-15.6V dc 3 sets of 8 screws, machine bolts on speaker, washered screws on front grill. Carlsbro PM65-100 , 1991 stage monitor amp-speaker , Carlsboro No repair as problem was in external feed. In exploration a 100R resistor next to TR7 was charred but functional,replaced with 1W. Replaced S M marked pnp TO220 trannies 1C04 with TIP41C and npn 1C03 with TIP42C. ( for 1C03 use RCA1C03 and RCA1C04 for 1C04 to find data ) Supply rails +-44V TR3,7,6 voltages -43.9,-.52,-44.6 -.52,-44.1,0.1 1,44,.5V Carlsbro PM65-100 , 1990 stage monitor amp-speaker Loud buzz plus hum and no power LED on front. Someone had been inside and fiddled because they had moved the header to front board one place out. So + feed not connected. Still a buzz when put in correct position or disconnected so presumably original problem was on main board. Erroded "dry joint" on -ve pin of the bridge rectifier so remade all pin joints. TR3 marked S M and 1C03 ? ICo3 ? 1C03 ? IC03 ? replaced with TIP42C as seemed to have been running hot for no heatsink. Carlsbro Sherwood Classic , 2002 Reported consistently low power 1994 JBR 23/2/1994 on the overlay but component dates seem to be 2002 and appearance more 2002, ser no. 80021.. (002 part =2002?) 2x MJ802, 2x 680R, 5W, 10R 5W 2x .24R 5W, 2x 29.5V, 2.4A Tx 2x .1R 1W, 2x TIP41C, TIP42C 8x TL072, 1x 071 philips C547B, 2x C556B, 2x C557 sp 3.8R 4 top cab sc plus 1 on Tx side Cut horn cable and put in a connector, slacken reverb cable cab clamp to release cable and unplug from tank, red to cab side return bypass contact cuts amp Poor clearance between prea pcb and chassis, resonance in use would easily allow it to ground out, without any pot nuts slackening, added spacers under main caps unglued 3x zeners probably say ST and not 15 B-E DVM-R of 100R on the 802s so perhaps cct similar to Stingray cct sc 4 at top and 2sc L&R With rear pwer level at max and pots at mid , GN-A, manual 400Hz 5mV in , 2.1V over 8R (main speaker line) 4KHz , 8.4V over 8 1KHz , 9.1V over 8 10K 50mV over 8R No problem found , on further querying , the owner expected feedback when using the guitar close to the speaker, he was not aware of the Phase control Rear HF cut, cuts the horn out. Needs celluloid sheet around chassis to insert amp into cab Carlsbro Sherwood ,1982 Parametric gain pot bad leading to bassy growl noise Bad send bypass sw kills amp nut and bolt missing from bridge Rect, replace and resolder pins relieving stresses Bad pot track rivet + grease 2x 2N3055, 2x10R 2x .24R, 2x40871, 40872 BC182 ,3x BC557 reverb 202R/30R wires to tank are crossed over and if wrong way round bad noise with turning up rev pot Carlsbro Sherwood tank 43R, white 184R no maker name, single conductor tails, bits of pcb show at phono sockets, both sides grounded. Remove amp front grill 2 sc and the panel with sp falls inward , so support on undoing. Carlsbro Showman parametric/1 , 1990 Blown fuses, shorted power rails used in very damp or wet conditions many rusted and seized bolts pa much like S600M without the triac cct on mains primary 3 blue and 2 or to other thermal sw C-E short on 2x MJ15024 and spalled .33R vitreous coating prea 2x560 ,2x270 2x15V mains tr 1.4R/0.2R Broken pair of output terminals. Replacement threaded sections too short for direct replacement. Had to heat up and bend the pcb to angle away from the rear chassis. Removed the fan delay switches as owner preferred to know the fan was working at switch on and always used loud. Red polyester .33uF, 400V between base panel and pa 0 rail. Terminal strip R 5, Gn 7, Y 10, Bk 11 6,8,9 c/s 2x 4u7,63V TIC263D, bidirectional diac/zener?, 2 caps ,47K, 2k2 on speaker protect cct 2xSM2718A,2x SM2177A , 4x .33, 10R 1W, 10R vit, 4588 on pa Beware stray wire filaments at the terminal strips bad 20mm fuse holders other ch 3way o/c SM2178 on o/p board replaced with 2SC2516 could not find a BUT11A or 2SC2373 powered up ok without 8R load but with 8R drew 1 amp of mains at 70 percent mains terminal strips DVM wrt pin 7 when rerpaired 1.9,1.9,1.8,-, 1.8,1.8,1.9,1.9 >2.5>2,5,2,-,2,2,2,>2.5 With mains at 55% main rails +/-30V 1 channel good the other one even with a 27 ohm load oscillates at 65 percent of mains and above, bursts peaking at 40 KHz dropping back to much lower f, extinguishing and restarting over 5 seconds or so. power amp probably much like Carlsbro S600M uses 4x MJ15024 , 2x SM2177A, 2x SM2178A each ch predriver DC levels (prior to oscillation) certainly different to the good ch but no obvious reason other than rain got into the amp A lamp will go in each of the +/- rails before I fiddle again Removed the triac speaker prot cct just in case a reaction with that, same result. Checked ESR of all cap types. Upto +/-40V rails , below oscillation, all DC agree near enough on both channels all TO3,TO220 and TO92, zeners. Go up to about +/-45V and the 6V, 5W bulbs start glowing that I added into the supply rails , alternately swapping dim and bright pairs very odd. Next I'll disconnect 1 of each complementary pairing of MJ15024 and see what happens. Still oscillatated with one pair and also with the other pair. Checking over the board again there was no continuity between line level i/p ground and the pa ground. An innocuous 1/4W resistor the same body colour as all the others but overlooked at 2.2 ohm bands was o/c linking the grounds. No discolouration except I managed to originally see the third band as yellow , not gold. No overheating on the adjascent pcb , so presumably a fusible resistor. In hindsight the slow "hunting" effect of the osc giving alternate loading to main + and - rails should have suggested a ground or zero problem. The "good channel" also had an o/c 2.2R but presumably because full o/c no oscillation there. The failed one in the oscillating channel had 3.7K across the ends so presumably not fusible resistors. Must have been a very high current surge to knock out normal MO resistors without any sign of overheating. Disc 1 input is sleeve of TSR of 1/4 inch socket, Disc 2 is normal tip Carlsbro S600M, 1981 600W slave amp Triac mains power protection, thermal sw on heatsink plus other stuff monitored presumably. Its in an awkward area to get to, a lot crammed in a small box. Carlsro badged TO3 audio o/p devices ERD1159 ERD apparently means Emitter Ring Diffused and MJ15024 is reasonable replacement. All h/s screws needed tightening but all unplated. Distinctive feature all sockets on the back XLR ,4 i/p and 4 speaker o/p one set of 4 female and other male. I cannot, cold, see how this setup works I'll have to desolder one each of the pairs of the th/sw (4 in total) , one pair for each ch , seems one parallel pair for normal fan use (in series to mains fan) and one higher temp parallel pair for overall cutout via mains triac. As all seem to be s/c cold, perhaps one of an o/c-cold pair is shorted. Then there is a triac crowbar on each output that presumably activates the mains triac, 3 triacs in all, to confuse matters So 2 n/o 58C th/sw in parallel for fan operation and 2 100C n/c th/sw in series for cut out. Can power up now having sorted that conundrum out. Power side works including the over temp th/sw system, now to somehow reconnect the signal lines. Unfortunately another problem became apparent. To avoid a 1 turn secondary on the torroid they passed the coach bolt through a second anchoring plate with some insulation. Looks like 2 cut down black plastic 1/4 inch socket outer rings. One either side of the hole in the plate, but of course not high temp plastic and have softened enough to deform , not actually making metal/metal contact but obviously not safe. Cut some PTFE discs to go inside the large hole and 2 pairs of sheets of PTFE either side to bolt down 7.6mm and 12.1mm diameters 100R via mains sw , due to triac cct primary 1.6R, sec blu/y .3R 2x 47R ww SM2177A +1 inside heatsink section SM2178A + 1 inside 4558 each ch TIC2360 as speaker protectors 2x 1500uF, 63V remove 4 screws outside air filter grill to demount whole power block 118v DC R/Bk at bridge R, for 228V on variac, later emerged this high V was due to triac control problem I was running on a variac and with about 90 percent mains and with no load etc there was 0.1 amp current drawn from the mains and a noticeable amount of transformer noise I took to be saturation noise and current drain, more than I'd like but until I could confirm with the owner about previous useage, I let be for then. This time I powered up and 1 amp being drawn with no load at only 70 percent mains. Disconnected the secondaries from the amp and still the same. Disconnected triac circuit and the transformer is happy to 100 percent mains, fed directly, and only few mA of current drawn. What can be going on ? To get to the triac componentry proper requires a major strip down first. Could it be half cycle firing and causing some sort of magnetic mutual/resonant/self-induction effect that is causing excessive current? A matter of isolation transformer and scoping some dropper in line with the primary to see ? No obvious heating on the triac, only a small heatsink. I was monitoring the DC last week and it was already a bit over the 63V rating of each electro. This time direct to mains, no triac, it was much more normal, forgot to note but about +/- 55V probably at 100 percent mains Scoped the secondaries and a cross-over distortion developes on increasing the variac voltage, not particularly strongly, but definetely there, and increases with voltage increase and "saturation" current/mechanical noise. Placing an isolation transformer on the primary with a 25R/20W dropper to "neutral" and scoping, then the problem was obvious ,now unfiltered by the transformer. Could now run up much higher variac voltage because of damping by the added R but even then there was 3mS duration spikes of peaks twice that of the mains ac pk-pk of mains (UK) 20mS period. So some sort of quasi buck boost inverter effect going on. What to look for around the triac when I get to it ?. To get to triac area, 8 XLR connectors with 3 stout wire standoff conductors each to cut, (then desolder both cut ends and replace eventually ). Because audio input and output and mains control all on the same board with no obvious isolation band between the sections I replaced the BC214 with a BC212 and as no TIC236 to hand , with a TIC226D for proving purposes, temp. There is now no sign of the broad spike trying with the 25 ohm dropper, even to 100 percent mains. The 214 tests as 420 hFE and I'll assume the triac is faulty. My triac test is little more than go/no-go, as only substituting in a lamp dimmer set up, so may well work with light duty and non inductive load. The 5.1V device tested as a 5V zener , I wonder why 2x 1N4005 and not 2x 1N4001 in that area. This is probably the circuit, split primary is used , ZD is a 5V,1,3W zener checked ok , V are 1N4007 checked ok, 2.2uF,250V polyester , pnp BC214 emitter to top , 94R is 2x 47R in series need equi-spaced font selected to read the ASCII image 240V | mains primary |C |C------- 120V ac---------------------------------------| |C | | | | 47R | | ___ | | -|___|-| | | / | | | , | | | , |< BC214 | | / -| | | / / |\ | 100R,25W| , / ------- | | , / | | | |----- / / | V 2.2uF , 250V | .-. _|_/ / | - || ___ | | | V_A / V ----||------|___|------| | | | / - | || 94R,10W '-' | | ZD | V |----| | | - | | | | |TIC236D |----------|-----| | | | | | |-------| | --- --220uF | 220uF --- --- | | ___ | |------------|___|- | 2K7 0 V 600W audio amp, runs perfectly happily if this triac stuff is bypassed. Soft start circuit Plenty of gain on the pnp, all Rs check out ok and triac checks ok tried out in a dimmer circuit. Running up the transformer , without any load, with this cct via a variac there comes an ac voltage where large peaks are produced at the primary and overvoltage at the secondary and nasty saturation type noise from the windings. Checked waveform on a scope via isolation transformer and monitored over 35R resistor placed in series with the primary. Peaks are one a cycle (about 3mS of 20mS UK mains) but not at peaks , troughs or inflexion point of the mains and amplitude of the peaks maybe as much as twice the mains peak to peak . Swapping the TIC to a lower rating TIC226D the amp (no load) works fine, no nasty mechanical noises. Swapping the triac to a TIC263M 25A, 600V the same effect is observed. I'm assuming that something is causing the triac to cut , once a cycle, when a high voltage is across the transformer and the inductance of the primary is generating these peaks. As the 2 220uF,10V were high ESR I desoldered them, to replace with new, but because new and old were short pinned radial format, I managed to solder in the old ones again. Replaced with 2 x 100oF,16V atop one another and shrouded and fine with 25 amp TIC, so left in there. Cut the standoff to all those XLRs to access pcb, replace with new afterwards In a closed steel case, no air cooling ( fan air is ducted only through the power amp heatsink ) and no passive/convective vents. Torroidal structure, no inherent saturation current with open secondaries and otherwise well behaved. What sort of plateau temperature would you expect if it was delivering continuous 600 watt ? Rule of thumb: 1 degree rise for every 1 watt with an area of 100 located in free air. Assume 95% efficient transformer 30W! Two layers, we're talking over 60 degree rise from outside air to inside torroid. Just an estimate. That was worse case scenario. I added a 110 degree C , 10 amp thermal fuse to the outer surface of the tx. Should never be run at 600 watt and there is some forced air ventillation as the amp heatsink is not totally airtight and slight holes around the casing, but these transformers were made without internal thermal fuse. (A way to measure INTERNAL temperatures in a transformer without having to dig into them: Run until temp is stable. Shut off and immediately start measuring winding resistance as a function of time. Plot the curve and recreate the missing section of plot between t0 to t1, where t0 is when you shut off and t1 is your first measurement. The resistance at t0 tells you what the winding temperature was. you need to know what the winding resistance was at room temperature to get a calibration point.) Carlsbro Viper 1992 no compressor, no EQ sp 3.1R IC4 CA3080 , others are 4558 Corroded and broken 1/4 in socket bad solder on comressor pot 3 sliders of the EQ corroded but renovatable, and no LEDs lit Uses 1 amp rated TO92BC640 and BC639 predrivers to 2x 2N3055 , not TO220 devices Cleaned all IC pins and graphic LEDs came on IC6 p1 -14V, p2 -.003, p3 -2V, p5 +2V,.06,+14.5V IC1 p1 0, p2 0, p3 0. p5 0, p6 0 ,p7 0 replaced IC6 and same +/-2V pots at 1/2 and signal in passive ip compressor at 0 , 400Hz in 50mV and compressor LED just lights compress pot at 1/2 , 215 mV in and LED lights pot at max needed 500 mV in with all pots and sliders at half and comp and graphic sw in 50mV 400 Hz in IC1 p1 and 7, .028, .32V ac IC2 .25V, .32V ac IC3 .25, .25V IC4 p6 .11V ac IC5 .24, .24 ac IC6 -14V, +14V with working amp With all mid pots and sw in , 400 Hz in then .95V in and PPI LED lights Carlsbro Viper bass combo, 1990 , 25Kg Pops and bangs then drops out after 20 minutes, starting ok again when cold. Vibration induced failed dropper joints at the preamp 15 zener supply rails. Redid droppers tied together with silicone rubber sleeving and silicone rubber support pads and replaced associated caps has one had probably leaked. Redid solder joints on major leads on pa as 2 would soon be a bit suspect. One 1/4 socket broken, the other weak , replaced with stouter types , upside down and cros-wired and located in place over the intrusive switch for one. Rails +/- 44V , with back plate horizontal and feeding with 400 Hz and o/p of 6W continuous, then thermometer in the heatsink back bracket stabilised at 75 degrees over 20 degree ambient after 40 minutes. Uses 2 x 3055, 2x RCA 1C03, RCA 1C04 2x .24 , 22x 10, 1K 1/3 W 4x 4558, 3x RC4136, vectrol linear optocoupler 2x 470 ohm Carlsbro viper, 1989 Buzz much worse on disconnecting the prea as no secondary ps caps then. Loose main cap Viper pa is supposed to be much like Colt 120 schematic Carlsbro Viper bass , 1989 Dropped amp. Hum,hiss and thumping according to signal level. Main rails +38V and +3V Broken pin and failed trace to another pin of the bridge rect KBPC602. Had to grind off the 4 outer rivelts and the 2 inner larger rivets , trice each as the centre blob barred removal of the remnants 2x 2N3055, 2x .24R, 2x 10R, 2x RCAIC04, IC03-C,2x BC 212 1x BC182A ? indistinct Extended the affected pins of the bridge with wire allowing plenty of slack. Rivets replaced with 2 different sizes of bolts and captive nuts. Carver PM 1.5A amp, 1999 Serious amount of damage on one ch from someone using handfulls of white goo under the TO3 ," insulating" the pins as they were inserted through it into the TO3 sockets, causing sparking at E and destruction of that socket and a load of colateral. Plenty of info out there Service%20Schematics-1.pdf eservice etc But nowhere can I find the ,no load, quiescent draw from the mains. I have bypassed / isolated the mains triac board and powering via metered variac to the transformer direct at these preliminary stages of powerup. Covering the pins of the proper mains plug . Running at 50 percent mains about 0.1 amp current draw and all monitored DC levels match between channels and clean signal on output and ps rails half expected values. Increase to 60 percent and draw climbs abruptly to 0.5 amp . So far quickly returned to 50 percent and nothing obviously overheating. Anyone happen to know the expected draw? I had to check whether I'd connected mains to one 120V primary by mistake as it was that sort of effect but without saturation noise from the transformer. Will return to it later today and also try engaging the triac section as I've not got my head around the on demand draw triac instead of good load/bad load or brownout triac Very awkward wrapped-up around itself amp to work on. With so many supply rails and 50 percent values I'd not noticed a blown up and shorted 3900uF,50V electro in the ps. Another 20 minutes getting that sub-board out, anything to avoid taking the whole amp apart with all those 24 TO3 sockets demounted , frail soldered-in interboard "headers" etc Most Rs around R30 burnt up. Q30 replaced MPS8097 with 2N3402 MJE2955T to BD912. Replaced TO3 socket , replaced a number of the TO3 and pulled and cleaned the goo off the existing over-gooed B-E TO3 pins 30 percent mains, high level distortion on pin7 of main interboard header array -34.6, -15.3,-9.9, 20.8, 0,-8.0,-0.2 good ch pin 7 +0.2V 470uF was s/c mps8099 ohmic replaced with 2N3906 40 percent mains DC at TL081 op up to 6V on bad, 0V on good 3900uF, 50V s/c in ps disconnected R21 and R57 vand checked V R21 49,8V and R57 -10.4V , 40 percent mains Polyester 10nF C7 shorted due to radiated heat from failed adjascent R30, 220R Reconnected both 4.7R and compared DC on good and bad ch at some main nodes Change bias pot setting to bring down quiescent current on the repaired amp 50 percent mains +/-63V main ps measured some main pa node V,both ch o/p 0.0, -62.3, 62.3, -3.6,3.6, 0.0 at 50 percent ps rails +/-63V, +/-18.8V, +/-27V, +/- 11.8V 15V on fan supply At 60 percent mains current draw jumps to 0.5amp, time to reconnect triac system With triac/magnetic drive 70 percent mains and .21 amp mains current First time of meeting this triac drive rather than protection concept Upping to 90 percent mains the current draw drops from the 0.5 amp of 80 percent mains to .2amp approx and fan revs drop 100percent about .25amp , main railes +/-122V .47V 400Hz in both ch , 9.3V over 4R each with vols set to mid What is the prognosis for PAT/insulation testing of these "magnetic field" amps, knocking out diac/triac etc ? with 3.9M, R8, between ground and one side of the mains transformer. Triac protection ccts are isolated from ground, IIRC, where used in amps. Survived previous PAT testing , 2M cutoff in UK Carvin Pro Bass 100, PB100 Blown o/p , maybe started with poor solder, hot spot, small burns at solder pads, device Carvin marked 60-72940 , replaced with TDA7294V 15 pin device to 10 wire ribbon H2 15V,0,-15,sig to pa H5 1 sig in, 2 gnd, 3 stdby, 4+5 + supply, 6+7 - ps, 8 mute, 9+10 o/p Carvin Pro Bass 100, PB100 Any movement of the frequency pot for mid band lift created full DC bangs. Ultra-miniature pots that have next to no metal for the wipers. I assumed gooey grease in the pot was sufficient to lift the wiper from the track which in itself had no wear. Decided to replace the pot with sub miniature pot but as overall length less, padded out with a block hot-melted to it and board and extended connections. Uses 4558s apparently dated 1983, although Carvin WWW schema for version B dated 1995. Used black 4 lead opto-coupler Vactec/Vactrol LED -ve at notch corner, cell at the other end. Used 15 pin hybrid 100W,100V labelled Carvin 60-72940, 2 large Rs, 820 ohm,7815, 7915 The rattle noise on moving the amp is a spare fuse in the IEC socket. The amp to speaker link needs the elbow jack replacing with conventional, just enough room. Poor mechanical connection at the elbow means a resistance and voltage drop, heating the plastic disc that is all that forces a mechanical connection so progressively worsens. Carvin X50B tube amp, 1989 Told the amp was not working Amp seems to work perfectly well, being repaired for minor problem , broken wire at the return of the external effects loop so not working if externally connected. no succeptibility to microphony or tinging distortion. Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? The amount of leakage apparently is no big deal for power tubes, if it gets below 100K then have a hum problem. I was wondering if there could be some sort of thermal runaway situation. Measured no more than 1mV rms hum over 4 ohm output for this one , level set for 2.25 W of 400Hz output, but disconnected and monitoring for shorted input. All pa W/W measured in circuit at about 350 to 380 ohm. 470K, 2W 5 x 4558 , 4049 + 4x 4558 240V primary 4.3R Secondary red , in circuit, 32.5R yellow/yellow 1.2R blue / gn 2.2R large gn wires heater supply H2 wire colours Bl,P, D Brn, R, Lt Brn, O, Lt P, Lt Blu, Bk,Y,Pk H4 P,P/W,O,W,Y,Brn,Bk,Bk,R,Gn H3 voltages 0,-15,13,0,13,0,0,0,13,0 470K , 10K Someone had been in there previously , maybe removed R arounfd the Master pot. Could not see why they would employ just 1p 1w of 2p2w switch and no use of the pot. Placed a 680K R where R13 on the overlay . Load test , thermometer wired to a 85mm pickle jar lid , balanced over the 2 bottles 4 ohm load, 400 Hz giving 3v ac over 4 ohm 15 minutes to reach 40 deg c over ambient and 0.06V ac increase Casio CZ 5000 1985 keyboard No function,LEDs or LCD display The only convenient 0V point for the TTL I could find was the -ve pin of the ps bridge rectifier. No 5V for the TTL. It looks as though the keyboard had been dropped as the large electrolytic on the ps had moved and consequently the track continuity to the 5V regulator part of the ps was broken under the capacitor pin,not obvious at al. With all 3 connectors unplugged and PA order on main pcb not the ps end which is different order. PA 0,15.3,-16,0,5.6,0,5.2,0,5.2 PC 0,0.03,5.2 PD 0,16,15.3,0,0 Casio WK 3000, 6 octave keyboard,2003 Intermittant loss of left speaker. Attended to all ps/pa solder points and conneections and desoldered headphone socket and remade. Open case upside down , from the rear first and then free the keys section. Work on it upside down with the keyboard section innermost. 3 pin TO126, device marked S2003 marked D for diode on overlay , only 2 of the 3 pins connected and diode and resistance test to the other 2 pins probably o/c so n/c ? All else functioning perfectly, but seemed odd using 2 of 3 pins. A nice stable 5V over the 2 pins in the ps area, so that a 5V, 10W (with heatsink) zener diode was my assessment. No heatsink used on this one but a useful TO126 format for say 10W zeners that are bolt-downable. Uses LA4636, 2x 2068,Sharp PQ1CG21H 3,1.2,0,5,14.8V NEC upD63200 dual DAC , pin 15 serial data in Al caps 2.2V, 2.7,5, 3.3V , SM tand 0.8V 2x wired caps on uPD65881GK062 gate array on underide of large board 4.9V Ami LP62S2048-70LLT 256x 8 SRAM ps to main processor board ribbon , starting red 5,0,5,.2,,01,2.9,0,5,14.7,5,1.6 (o/p signal line 1),1.6 (o/p signal line 2),0,0,2.7 D shaped recesses in case for washered screws On first powering up it plays dumb, display echos the key presses and midi functions normally but no sound out of the built in speakers unless you wake it up going into demo mode for a bit. Nothing wrong with mute/standby functions of the main amp and low level hiss from the speakers so not headphone bypass problem. Possibly on powering down "local off" setting for midi use is stored in the memory. Seems no access via the keybpoard/keypad/buttons etc to alter this, must be via an external pc/midi link. But just pressing "piano setting" resets a number of things , one of which is setting local to ON (if OFF), in the troubleshooting guide , if you have a silent keyboard. This Keyboard not used via MIDI But there must be some powerdown (or power up ) fault creating this random occurance (left unpowered overnight and powered up perfectly ok, despite deliberately switching off at the mains rather than powering down via the power on/off button). No obvious on-board battery , although overlay symbol and unpopulted section of the main board has this for some other model type. The corrupted memory is on 'song memory', keyboard ges silent after the owner pressses that button to recall previous recordings. Probably corrupted when writing to it when someone pulled the DC supply plug out of the back. Citronic Digi 16P mixer amp maybe 2007 Hopefull ps bad/burnt solder on a 2W ceramic resistor , double sided board and soldering, or not from the reverse side, the trace on the blind side, as obscured by the resistor. +/- 155V on mains bridge rect Anyone know of the SWPS schematic or is Citronic rebadged as other names? The SMPS controller (seems to be outputs via a few predriver TO92 to 2x TOP3 powerFETs across the rectified mains) a SMD IR2156S which according to the datasheet is a flourescent tube electronic ballast and igniter, no mention of use as a SMPS, with obviously no igniter requirement one hopes. "American Audio" seems to be related to the Citronic name but exact cross not found It should have been a simple job. Intermittant drop out. Look inside powered up and the ps fan is obviously defective, so fits the symptoms. Fit a replacement and power up and not a dickie-bird. No led flicker or fan kick. Undo the ps and obvious dropper solder problem underneath. Sort that out and still nothing by monting on pillars. Checked for topside mixer and power side earth continuity if that is required. So what else have I disturbed? close inspection reverse-side looks fine, topside is heavily populated and very few solder points can be seen. Continuity to the pa monitoring thermistor good. Enough power gets to the main bridge rectifier for startup supplies but the relay does not click over that shorts out the droppers for full mains current, let alone anything else. This is a "Hailin switching power" DWP1070 power supply but that got me nowhere. From the IR datasheet Vcc is enough to get the controller started and both control voltages are the right side of thresholds for operation so a mystery why no oscillation. The relay supply is taken back across the HV/LV divide, rectified from its own winding on the switching transformer, so no oscillation , no relay click over I misread the datasheet , not enough Vcc for IC startup. Local vibration from me must have been the camel's straw for a hot-side, luckily industry standard voltage regulator once I could read the label, and its downside electro, after having been cooked in service. Replaced and we have power again. IR2156 p2 - p3 connected and p5 -p6 connected, following in fault mode p9 to R16 SD <4.5V p10 to R33 cS >1.3V con 3 is just DC supplies Vcc 5.3V another time reading p10 <> 0 , p9 4.2V R21 probably 33R had a corroded/flaked end 7815A VR, 23V on ip 4.3V on op replaced it and low side cap 27V, 14.8V fans -12.7V red to -12.4V and bk -17.9V , nowhere near 12V warming the TC1 seemed to make no difference only 5.3V on fans +/-83V on main rails LV HS device DC readings 49.8, 44.8,56.5 4.9,0,12.2 14.90,18V -14.9,-18,0 BCE, -12.1,-2,-12.7V dc Untwist pa power and speaker and ribbon wires Now to take some quiescent DC readings on ps coldside and one of the PA as there is nothing technical out there on these amps. So fluourescent supply ICs can be used for controlling power amplifier SMPS Tx 266R between PTC+ and - , marked TC1 near the pa ribbon cable 10.1K and 10.6K on reversing DVM probes on airpax ps temp sensor Mains to 2x large black thermistors? which are bypassed the blue relay contacts when energised On demand 12V fan control Under therrmistor control. If at power up the DC voltage is too low to start the fan can you always rely on the fan starting at some point with a slowly increasing voltage or does it depend on the make/design of fan ? 3 fans fed from the same varying supply. 2 large , one small, all nominally 12V. The 2 large start with the applied "cold" voltage and eventually the small one starts with warming of the amp . Checked by slowly powering from a bench ps a few tmes . But I randomly picked up another new fan that I had about and once out of 10 or so times it did not start by the time it had reached 12V. I decided as this amp was never used for low power use that I would disable the ramping and set it on maximum drive always, not worth the risk/inconvenience of stressed components/mid-performance chance of a cut out. Q4 and Q5 and 2SD669 on hs is fan control. Added 160R to bring PTC cold resistance up to 460R but made no real difference. So made open circuit for full fan on voltage of about 11V From start up mains relay clicks over about .5 sec in and pa relays about 2 sec in Replaced the seized power supply fan with 2x 40 mm 12V, .1A fans tied together using one of the original tapped holes and a piece of paxolin board to the other tapped hole and keeping the fan bodies away from the mains side heatsink Probably the worst bit of "soldering" i've ever seen. An intermittant fault with one channel speaker lines 2.7mm diameter over the insulation, 1.5mm or so core, the 4 wires go to a rear board for speakons and 1/4 inch outlets. Each wire is stripped neatly , leaving some whitish thin coating over the copper core wires that probably holds the filaments together until solder temperature melts it . Pushed through the large holes in the solder pads and "soldered" on the blank side of the board with little blobs of solder relying on melting of the board composite to hold in place, and unmelted coating plainly visible on the other side. I assume the holes are plated through or there would be no electrical connection possible. The assembler must have soldered the wrong side. PA, red blue speaker wires (outside amp) with 8R on output TOP3 DC readings -5.7,-83.4,-5.7 x2 -6.2,-83.4, -5.7 x2 .5, 4.7,.03 x3 .2,-5.7,.03 x3 D22 -5.7,0,-5.7 Q34 -6.7,-83, -6.2 Q in 3 columns of 8 , 5 and 3 off, outer pins only as tight to pcb 1.7,2.3/ 2.7, 1.1/-1.4,.8/ -1.4, -2 / -82, -81.4 / -82 , -81.4 /-82, -81.4 / .6, .06 / .03, .03 .03,.03 / 81, 81.6 / 81.4 , 81.6 / -82 , -81 / .6 , .06 0, .6 / .01 , 0 , .06, 0 Citronic SSL 1001 Sound-to-light unit No lamp function on any channel Fracture of a pin on 4025 due to corrosion at juncture of legs and solder.Other ICs looked similar so removed all and replaced with socketed new CMOS ICs.Note for personal safety when working on the logic circuitry disconnect from the mains and power the logic between Vss and Vdd from a 10V bench power supply. CME UF60 USB/midi keyboard stuck control sw buttons 4 long screws on long side of corners 2 close under front large gauge m/s plus central pair, recessed are large pk hold keyboard. Beware clipped on wire to underside panel. 2 x Zn pk under front brace then unplug and mark 2 wires before removing. power-in board 3x Zn small to rear 2x Zn large to pillars 2x L7809, 7805 sw panel all Zn , 2 large standoffs power i/p socket bad , ring of gunk in the socket, "reamed" out with 2mm drill mark main pcb standoff pillar orientations as offset Added 6 1mm thick nylon spacer washers around the main key pad. Refix this end first of the long pcb , probably shifted wa scausing key jam. The small pcb with 8 and 16 MHz xtals , 4 way conn is bodged into 6 way conn shifter towards rear panel. Stuck key via D to p15? + p18? (no obvious index pip) power in board PbF needed soldering top and bottom To stop Transpose LED flashing do a factory reset of Octave + Transpose while sw on Cort GE15B Loud buzz all control settings Probably "bathtub curve" failure as Googling this with TDA2030/A or hum/buzz threw up nothing. Or maybe swarf around o/p device ragged bolt hole so cleaned away the silipad and replaced with mica and new TDA2030A. Failed p3-p4 20 ohm. LM13700M as SMD with DIP conversion 470,4R7,2x 150 3x 072 speaker 5R5 Remove amp through front slot Crate BV150H Gets excessively hot Draws 1.2 amp mains At 85 percent a 6L6 measures 0,0,-5,0,-38, 377,379, .5 -69.1, -29.4 over R21 100 percent -79.4V at D17,D18 16V 10,000uF C64 domed end so replaced with larger cap needing shaving back J2 connector If you can unscrew overhung screws then only the prea V pcb needs removing to change cap Added 51K over 22K next to bias preset like the 15K of a BV120 100 percent mains and .8 amps a 6L6 measured 0,-4.9, 436, 433, -48.6, 0, -4.9,0 mains Tx 2.1R// Be 1.2, or-or.9, r-r 6.9, Gn .1 op tx 13.6, 11.4 Changed mains neon dropper That was "lighthouse" neon 47K dropper for 110V used in uk on 240V. Same with this one needing the mains switch changing , charred and part melted sw cover this one but holding up at 47K. This one been run too long with insufficient bias and run away red valves. Crate BV150H, 2003 ? Blown fuse blackened barrel, replaced and then intrusive hum developed After testing all valves and on removing could see a dark opaque patch on the inside of the glass envelope. Broke in by sawing off the bakelite locating spigot and using a hole punch on the evacuating pip and found a bare metal patch on the anode/plate , otherwise grey coating. Breaking into that there was a patch of missing white coating on the cathode opposite this patch. Connection between cathode and G3 is fused / broken link , presumably very high current passage cathode to anode, what could cause it and how much current could pass ? Before I broke in the getter was usual metalic black appearance The getter in the cap is now white caesium oxide or whatever (in a sealed bag i might add), the black patch is still matt black. A square patch on the envelope, square because that was the boundary although not extending to the glass, looking like a spray paint squirt but square rather than round I would say the patch on the anode looks as though it has thinned but not punched through, so perhaps the metal plus whatever the grey coating is condensed onto the envelope. No trace of white in the getter on the cap until a few minutes after I broke the evacuation pip in the base The opaque patch was constrained only in the section of glass containing the section of anode with the burnt patch. Neither mica spacers or plate metal fully close the gap to the glass so any of this material could have gone through those gaps but didn't. This sugests to me some sort of directed jetting action. Normal more metalic looking getter cap coating at the top of the valve was still present before I broke in. All 6 6L6 were of the same batch and none of the other 5 had this side opaque patch I cut the pins at the base of the envelope to see into that area under the cathode column and the ribbon that connects to the cathode tube is spark eroded ? to a break. This ribbon is 0.5 x 0.04mm in section, if it was copper then the rupture current would be about 6 amps Mains transformer g/g 0.1R, r/r 7.1R, or/or 0.9R, bu/bu 1.8R o/p tx 11.4R/13.9R pa 6x 1K, 2x 30R, .1R, 2x 150K, 220K, 4K7 preamp 6x 10K, 1R Mains transformer wire colour coding probably like Blue Voodo 60 (BV60) but this one 4.5x4x5.5 inches, audio o/p 4.5x4x4 and no choke With 7 mains primary wires set as Bl+w/w/bn/V and 199V as mains then 5.65 V on all 8 +6 heaters and 407V HT1 and well over 6V ac on 240V. According to owner , bought it off company rep a few years ago and is export version prototype. Blew a fuse a few weeks back , runs still ,after fuse change (self heeled cap?) but excessive hum. 450V rating ps electros but I measure 488V on the HT rail and varying ac (4 to 5 volt ac measured via 1uF, 1500V polyprop), perhaps seriesed-up, but 3 in there. The neon lit mains switch looks more like a light bulb , runs too hot to keep your finger on, I suspect droppers for USA mains inside. No serial number on the chassis No mains voltage stated at the IEC inlet, just fuses for 110 or 240V, 7 wires to the primary side of the tranformer and jumper spade matrix inside. As the rep was going around Europe , not just the UK . Powered up and looked for voltages off from 0,110 or 240 . No smoothing choke for this amp it would seem, unless its in with the mains transformer . As the mains switch is made for 110V use then anything is possible I should have said previously only the 110V and 230V fuse ratings stated on the chassis, not 2 separate fuseholders, so someone might erroneously think it was an "intelligent" ps , no external selector switch or helpful labelling of selector matrix inside. All valves test ok except one 6L6 which, apart from heater, is totally dead, no gain at all at any anode current. There is opaque stain on the envelope in area above pins 4 and 5, localised in that area, although it could pass beyond the non-round, mica spacers. I assume some metal melted and evaporated/jetted onto the glass like the getter process. I assume this could have been plasma arc to anode and excessive current and blown mains fuse, as that part of the amp history. What would have happened here ? I will break into the base/glass pip/cut-ring the envelope and remove the innards to have a good look as presently cannot see anything through the deposit. A melted hole in the anode? what would physically stop any valve action? the getter is still silvery. Not yet retubed (that one plus another removed for balance) and tried out on reduced mains yet. Other than heater continuity it tests as though no valve placed in the socket. Same colour code of primary, not secondaries , as that blue voodo and seemingly the same significances. But I'll have to take apart to check what is jumpered to what, and also the HT1 smoothing is different as it uses 3 , not 4 caps there. I forgot to check each voltage on the 7 primary wires, will do so next. With the duff 6L6 and one other removed Putting 199V on the existing setting of primaries gives 5.65V ac so suggesting 6.53V ac if 230V fed in on existing internal set primaries. Is 6V ac on that Crate BV60 schematic a strict ie +/- 0.1V, or nominal 6V (with all 14 heaters supplied presumably) Also 199v "mains" gives 407V HT1 The hum is present but with my variac I can lift the ground and doing that, the hum goes and amp works fine , normally testing an amp there is no hum and lifting the ground can introduce hum , so I wonder what other problem lurks. 1000V megga test on the mains Tx shows nothing amiss to ground. Looks like the same colours but not necessarily the same taps. Monitored the total primary resistance and marked, removed/replaced spade connections until 3 spade connectors blue , grey and black removed without affecting reading . Leaving blue+white stripe, white,brown and violet as the primary. Powering up on 199V wrt to neutral the free wires read blue 190.3 grey 86.4 black 206 wrt live blue 8.3 grey 120 black 8.8V is this the setting for 210V, 230V or 240V ?, I'm trying to get the maximum number of turns as the primary. I'm thinking I need to swap the blue+white with the black lead. If complete agreement with that Blue Voodoo 60 then the existing wiring is undefined on that chart, the J numbering does not tally with this one Broke into the 6L6 , I thought the caesium getter went white immediately but takes a few minutes, envelope safely sealed separately now. The outer grey metalwork anode had a bright metal spot adjascent to where the black envelope staining was. Cutting half the anode away revealed a bare metal patch on the otherwise white coating of the cathode, no pools of metal or smoke trails, G1 winding looked fine. I'm surprised how tough the mica/composite ? spacers are compared to similar I've seen inside toasters Exploring the 6L6 a bit more there was continuity between the base pin and G3 but the internal contact to the cathode was missing. Presumably a deliberate weak fusible link in whatever occassions a plasma arc strikes between cathode and anode. Looks as though the hum was associated with the input socket. This is designed to be isolated from chassis taking ground from screened lead. As it was turning round with tight bush nut I assume someone had been in there and changed the insulating bushes about so ground-looped, now isolated and tight and no undue hum. Looked under the pa board and it is 2 seriesed 47uF,450V for HT1 and the other one with a dropper for another HT. date 2003 or later. Mains primary now set for presumably 250V as heater readings are still a bit high. So with full mains on there and all 8 12AX7 and only 4 of the 6 off 6L6 reads quiescent 6.6V ac and 470V HT1 from 356V ac, other secondaries or/or 32.8V ac and bu/bu 66V ac. Incidently not only the neon /sw needed attention but the handle is crap and jagged sharp metal exposed inside, covered with nylon spiral wrap, then expanding nylon sleeving and then 2 layers heatshrink all under the covering now I cut the pins at the base of the 6L6 envelope to see that area and the ribbon that connects to the cathode tube is spark eroded to a ragged break. This ribbon is 0.5 x 0.04mm in section, if it was copper then I make the rupture current would be about 6 amps. Presumably failed at a weld spot so less than that Changed to black /w/bn/v probably 250V setting and 3 other leads left taped over and tied off the board. And perhaps bk/wh/bn/Vi 240V and bl+w/w/g/v 230V Blue wire interconnect "ribbon" pa-prea 395,0,0,17,0,-17,0,0,10,26 and white -6,7V 2x 4700uF,25V under pa board As not 2 replacement 6L6 at hand, temp added 3.3R over the heater supply to check and this gave 5.8V ac Crate BV150H Intermittant loss of throughput Sovtek valves problem Likely a commonly occuring problem on the discrete wire IDC connectors, this one 2003. The core and insulation of the screened wire is too thick for the IDC metal. Presumably the IDC metal relaxes and only marginal metal contact to pass factory tests in the first place. Only light finger force required to lift the wire out of the trap. The screening contacts are fine, as just heatshrink sleving on them. There are about 10 such screened leads inside , with an IDC on either end. I suppose the probability of 1 in 20 failing is quite high. 1 & 5 J8 connection bad ch 1 select sw Technique for replacing 6L6/5881 o/p valve tubes I have large hands, how do people with small hands/short fingers do it? Just managed to break the top of one of these bottles. I thought I used the right tecqnique but failed here. Sovetek, GT badged bottles , instead of domed top, nominally flat with a bit of a central pip. Come replacing I go in the sequence , along the line of 2,4,or 6 sockets, that allows a full finger each side of the dragon's teeth grips to depress while pushing in the bottle. Then I place with top of the valve in my palm and push down on the ledge area of the top of the bakelite base, with finger tips. Doing so , the palm of my hand is barely touching the top but enough pressure on this pip to induce failure. As such a light force , I assume it was likely to soon fail from vibration & temp cycling. Failed in the ring around the flat area. Next time I see flat tops (flat not compatible with vacuum) I will cover with a temporary grommet, before replacing, any other experiences/tips? Perhaps change technique to making a yoke to push down on the spring retainers , using chest , forehead or chin or something, and then use four fingers on the base to press into the socket. Or some sort of chassis clamp to depress the clamps. Then two fingers, unless a weakened socket, is not enough pressure to overcome the resistance Or ignoring the scratch marks made on the base , and push in with 4 fingers on the base, after all it is only cosmetic damage. I don't remember seeing these sort of central pips before (on that end), either domed or flattish. Next time I will have a couple of strips of PTFE looped around the dragon's teeth and push in with 4 fingers around the base. Then releive each spring in turn to retreive the PTFE. If that does not work then have to make up some sort of spring compressor or let them goiuge away. It's just that years ago I came across an amp that the owner loved rotating the bottles about and the bakelite was a real mess, barely functional Crate BV150H Serious mains hash noise, more than hum, especially on the 2 non-clean channels. Repeat problem due to those flimsey IDC connectors, see above. A number of (variable) ohms in the ground path between input socket and chassis. 2 screened wires and 4 IDC connectors between input socket and a decent ground line. Pulled back the pathetic plastic IDC sidewalls, stripped the PTFE? sheathing and soldered the grounds to the IDC pin. Not heatshrink sleeving as above , but soldered both signal and grounds this time Crate BV150H amp Second one I've come across where the standby lamp thinks it is a lighthouse ( for a short while). When cooled down the neon's now black internal dropper , 1/3W or so, measured 550R . The switch housing says "110V lamp", surely I'm not the only one to have come across this issue. I don't have the schematic for the 150 , the BV120 schematic has the neon on the HT ac side, not the rectified and smoothed side. What is the work around , separate neon ala Marshall valve amps etc. Low side of HT neon returned to odd valued 332K in ps. While at it, the mains-on neon is also set for 110V like the other BV150H . I'm in 240V land and that will need accommodating as well. This one 2003 manufacture and without attention, that dropper will go pyrotechnic in ten more years of use also The paper label at the mains fuse says "U EXPORT 240 VOLT" Strangely both sw marked Arcolectric , England and 110 lamp, generally only building site kit would use this in England. Mains one discoloured enough so impossible to read colour bands measured 47K so both set for 110V presumably . Replacement ones have plenty of space to change the dropper, 150K as original for 240V land , and the HT standby 150K dropper replaced with 560K//560K o/p tr HT side 14.1R/11.7R some of the cable /spade connections at the mains section for 240V NC,Pu,Bk,NC,Br,Be thin W, thin W, W,Bn,Be,W, thin W or,y,or Be,Be red-red 335V ac large R54 100R using 332K R to ground then the HT neon can be 240V set neon 15K between V2 p6 to J13 100R 5W to 4K7 R55 to 10K R80 on prea via umbilical on line neares pa 256V , 236V at R80 on low mains 80 percent 345 and 291V 95 percent 430 and 356V Standby sw goes between J33 and J38 o/p tr supply to J38, relieve springs in screening cans Crate GFX 65, 1999 Triple footswitch , no name , no ratings on switches. Impossible to use as a mind of its own which channel it wanted to be in. On resistance anywhere between 200 ohm and 100K on each of them. At least easy enough to get inside them, dissolve away the grease and deburr the rough edges and put back together again. uses .2, 3x .47 plus 4 1.5K, 3.3K,220, 2x10 5x 072 TIP42, TIP47 7x J175, 3x J112 primary 11.5R , secondary .5R, 60V ac Crate GFX 65, 2000 Green LED but no sound on Clean channel Someone had been inside with a power drill or something doing some "repair" and stripped up tracks and board. In particular the trace that goes past near the input socket that they were trying to "repair" With clean ch controls at 1/2 and 14mV, 400Hz, at input and DSP board diconnected IC1 pin 1 56mV , pin 7 360mV IC3 , pin 7 40mV TIP42/147 , 2x 047 ?, JE340 2x 270, 470, 0.2R 220, 1.5K, 3.3K, 10R 1/2W Remove 4 heatsink screws and 2 pcb screws and DSP board to release the preamp board IC3 pins 6 and 7 to clean level pot and IC1, pin 1 the trace to th eclean channel For testing needs a ground connection to both the pcb ground points, PS and signal or nasty noises. Crate GFX 65, 1999 crackle output loose input side gnd sc, probably from owner loading down the i/p plug to "cure" the problem which was at other end of board , the int/ext 1/4 in socket diverter soldering Crate GLX65 combo of 2004 Uses miniature pots with clear plastic shaft and illuminator bulb inside the pot. Body 10x10x5 mm and even then space inside for a wire-ended bulb. The spindle made of clear plastic to conduct the light into a knob with red plastic inserts. Anyone know of an independent source of these. For future reference, as in for mechanically broken switch, all the pots are fine. Only 4 years of normal use and yet again flimsey push/push switches are falling apart. Replaced those with robust conventional toggle switches, enough room after bending the pins, wired across to the pcb, and only SPST use although they are DPDT switches. The mute switch is of stronger style. The compact LEDs illuminate the surrounds and the pot bulbs illuminate th epips in the knobs. 3 screws at rear release the prea section from the rest. Mark ribbons for orientation etc, to relese ribbons push the clusure strip. Reconnect cables before rejoining metalwork, double check you don't have 2 wires entering one socket, very easy with these lack of terminations. DSP footswitch mono, solo/clean/rythym stereo 1/4 inch Tx 55R// .9R,.9R pa 0.2R, 2x 270, 2 x 0.47, 220 2W, 1.5K 3.3K 1W TIP142 TIP147, 072,JE340 prea , foam cylinders go around stemmed LEDs Tx 55// 1R , .9 , .9 lights 40.5V at switch grey ribbon 3,2,2.5,3, .9,40,0 rhythm + dsp -41,0,11,.8 Crate GLX65 , PbF problems Multilayer ceramic C1 at the i/p prone to piezo microphony noise Mains primary for 240V Grey and white, 11.5R. In line , not 2 or more separate primary windings, DC ohms to nearest 0.1 ohm. Labelled by me as A,B,C,D,E crossplot (message souce maybe equispaced font) --- A B C D E A --- 9.2 8.5 12.5 1.5 B 9.2 --- 0.6 3.6 7.6 C 8.5 0.6 --- 4.2 7.6 D 12.5 3.6 4.2 --- 11.1 E 1.5 7.6 7.6 11.1 --- This is a single primary made for / in USA for export so wasteful construction as only parts of winding are used for international variants , not 2 separate primaries (with perhaps minor taps) Loss of output Pulling right side of front panel and hiss drops in level but pa hiss rremains. Breakthrough of VCO ? at low level. Most of the 1/4 inch sockets use switch function and poor solder points Crate GT212 amp , 2005 Mains hum problems speakers together present 3.2R Second time I've come across this prea ground connected to casing and separate pa ground connected to casing via standoffs to metalwork. Underside of pcb large solder pad, upperside 2 pieces of tinned copper wire. The underside solder seems to compress , maybe pcb as well, and then exceed the give in the star washer and looses good grounding. This time prea end , previous time was pa end problem. This time will solder brass washer on underside,each end, solder just between washer and board , not standoff touching surface. Declench the 2 nylon standoff and push out rearwards, last to reassemble Replaced input socket , wired in, mechanically decoupled from pcb 2x TIP47,TIP complement Mains antisurge ? TI? 155P UE1015 28R cold 072 ICs only 5W 4x .47, 2x 270 ,.1R 1W 1K5, 3K3,330,2x 10R Triple footsw so bet 1 &2 goes to C/S/R on amp and 2/3 to reverb, mark with stickers on amp and sw Tr connection layout for 240V Or Or W (1/4 turned) W W R - Gn Bk - Bk R 8mV 400Hz in on clean ch with pots at 1/2, .58V over 8R load over o/p device complement pairs 1.24V,36V,.16 // -1.02, -36V, .05V +/-16 V opamp supplies Crate Stealth GT-100H no output trying with 70 percent mains , with a signal in just a buzz in sympathy with vol and pitch of the input coming from the op tx. sp imp sw out of posistion Switchcraft EPS1 slide switch 4 amp rated and doubled up as used in Crate GT 100H Stealth output impedance selector. Amp grumbling by buzzing in its op Tx and no output. The selector sw had vibrated into the "off" position. Easy to get into and there is no detent spring + ball or toggle flip-flop contorted torsion spring mechanism . In fact the natural position of this switch is between the 2 states with the moving contacts between the pairs of fixed contacts, ie off/ no contacts, only the contacts themselves hold the slider in posistion when manual moved. A huge slot that would take a carpenter's 3/8 inch screwdriver but only requires a jeweller's screwdriver to shift, at 300 gm of force to move one way and 600 gm the other. Now I know what to do, just a 1/4 hour job to retrofit a dedent. Rob a spring and ball from a standard slide sw. 2 grooves ground into the inside of the fixed body of sw and hole drilled through the sliding section opened out at one end for the ball , the end of the spring glued in place and ball in-between static and sliding sections. Unclip an end to sliding section to get inside, nothing will drop out or spring out. these things this one now has a delatch force 600 gm one way and 800gm the other. As an easier retrofit fudge perhaps a disc of rubber, sandwiched at either end by the mounting screw, would bind the slider well enough to the chassis and still allow movement The ratings are embossed on the sw body but where the pins cme through, so manufacturer must mark the chassis. For 110/240V selectable equipment only used in the UK at 240V, I often insert a bent solder tag between such sw and chassis at a mounting bolt, to lock into place. Too easy for a drunk musician to change the sw trying to repair faulty kit. But this use is for a relatively high speaker current slide switch rather than mains op tx 26.5 and 34.4R either side of red HT wire Reverb tank both ends o/c, Accutronics 8BB21C1A. Amp had been dropped as both Tx had bend bracket supports pcb slots either side of the anode pins of the op bottle anodes Unwound tape of the tank coils by pushing through with a small screwdriver. The 27R was broken at the surface and simply rebuilt but the other broken at the core. Unwound the output one , but it got knotted so no turns count. But it did measure 198R and .06mm with micrometer Former 4.3x 2.6, 6.8mm wide turns maximum 7 x 10mm until touching the iron laminations. all too small to set up on my coil winder so went back to hand-drill with oddly 56 to 13 teeth gear ratio. Set the plastic former on the stem of a pop rivet and mounted in the drill jaw. Measured off 43m of .07mm wire and "skeined" onto a block of polystyrene so could rely on airbreak as back torque, ie minimal. Bubbly cut edges of the block are ideal for holding the fine wire without it slipping off. After pushing a thin rod through the block and setting in a small tube on a clamp. 510 x 56/13 turns so 2200 turns. Measured 261R so less length and turns next time , just as well as with vinyl tape over the coil was touching the iron on reassembl;y. This one with 1.58Vac over the 27R maximum output over the other coil was at 300 Hz and 24mV over 266R. Other way round 2.66V , 300Hz over 266R gave 1.5mV over 27R Running fingernails over the springs gave DVM ac 10 to 20mV over 266R and 4 to 5 mV over 27R Crest Audio Pulse 2 1100 power amps, 1999 Owner has 5 of these and 3 have gone into protect mode, all the same symptoms. All look the same but not sequential serial numbers. He's getting someone technical to look at the speakers and leads and as they are used from a diesel generator maybe a problem there. All failed in use , not abuse, not failing at switch on , and no earlier odd noises before failing. Anyway these 3 amps show clip LED on both ch, and then drop into protect. I've looked inside one and all healthy appearance. SMPS fires up enough to deliver about +/- 100V rails, both ch, for half a second , fans ok and relays click over but then drops into protect. No excessive mains current draw at any time. This one and the others , both channel o/p measure about 13 to 15K to ground and not tied to + or - rails so will assume PAs are ok at this stage and maybe falsely going into protect. Goes into protect mode at switch on. Useful info and schema on these G class amps as well as schema only, on e-service One smps supplies both amps and 4 rails, each rail supplies both ch, I've cut the "overdrive" rails temporarily and running on +/- 60V. Output has about +18V on ch1 for about a second before dropping down to 0, so o/p DCsense line to the PIC tells it to go into protect, of whole amp. With 15R load then op jump is to about 10V. The other ch2 is fine , no more than 0.5V on output loaded or not. Same 2 (4 in full operation) rails supply both amps. All electrolytics check out ok. Problem fault tracing is 3/4 of the active in this amp shows the same 18V or so jump at power-up. Disabling the protect line, so the amp powers up, shows nothing amiss after 2 seconds, on all main transistors, running at +/-25 V rails anyway. I will repeat this now at +/-60 V but as no 1 to 1 correspondence of device numbering or posistioning between ch1 and ch2 a bit awkward and I don't expect to see any substantial DC differences as has settled down after the first couple of seconds. How to zero-in to the problem device . Nothing untoward at the pa input but I will tie to ground the next time of powering up just to confirm. Looks like all 4 off 1M , need replacing, all those matching operational position of R182. Has 80 V in normal use over 1/3W 1Meg and used in dampish conditions is enough to make it go high or even o/c., not removed it yet. In an area of circuit not easy to measure or even compare ch for ch. Hooking another 1M across it is enough to give amp operation without disabling the DCsense error protection. Its this R that takes the central biasing section low at power up before the Tr25+C53 section becomes operational. At least the schema are around. Some notes in passing, you have to be careful how you pick up that large pcb , by the heatsinks and front metalwork not by the edge or rear as those large piercings make it weak. Discharging the rectified mains DC cap of course. Maybe all component oles( certainly the 4 off 1Meg Rs) are the size for power transistor legs or IC-pin eyelets so although plated through holes , minor components like 1/3W Rs have a lot of solder around the leads so libility to cracking I would think. Not actually the 1meg failed it was the TO92 over the complementary 1meg gone 35uA leaky, pulling the zero point upwards No screws to Speakons. Remove inner screws rear and under. Leave front panel and handle plate in place. Undo bolt and nylock hidden under wiring cluster Handle via the front plate , heatsinks and transformer at rear, not the pcb as large piercings must make it weak. Cable tie the output subboard in place to protect header pins. Add XLR barrel to protect the exposed orange connectors Break sp16-27/19-20/22-23/12-13 Add 470K over mains DC caps for self protection should you forget to discharge. As large and unsurrounded board it is easy to drape solder over something. Knocked out TO220 device doing that ,leaving non working SG2525A , Vcc of 5.9V wrt livegnd, shutdown at 2.5V , Vref 4.3V 7.2V on ZD2 at standby. TR48 pass tr TIP121 CE short , replaced, lift clip slide ptfe under clip before sliding along the channel, in reverse pull and slide the clip over PTFE With 1uF 630V caps on the 4 power rail cuts , 2 to 0V and others to appropriate points , not zero measured -82V,80V,162V,-160V There is no 1 to 1 correspondence of ch 1 to ch 2 TO220 chains on the h/s so marked A to I on side 1 front to rear and 1 to 9 on side 2 Correspondence is then 1E,2F,3D,4A,5B,6C,7I,8H,9G but beware of face reversal Placed 130V 20mA bulbs across the 4 breaks initially. IV for intermediate rail volts and OD for overdrive volts +/-IV very dim <>4mW +/-OD bright <>10mA soon drops into protect then short duration operate +/-42V, +/-110Vwrt 0V 28,57,-34,-54 removed OD lamps +16V , -27V IV rails +/-15 V regs ok TO220 voltages with the 130V lamps in place 1 to 9 18.8,18.3,19.1 19.1,18.6,10.1 19.6,19.1,19.6 -23.7,-24.2,-23.7 -22.7,-23.7,-23.2 -22/7,-23.7,-23.2 19,-2.2,19 -2.9,-2.0,-2.6 -22.9,-2,-23.3 Apprx .1amp mains draw at 240V PIC protect line voltages in this situation Current, -13.6 at R49 Error, 0.01V, R10/R13 Brownout 8.9V, R34 DCsense 4.6V, R21 in protect -2.7V at R49, 0V at R13, 8.6V at R34, 3.7V initially at R32 (leaky TO92 problem) Brownout signal for various mains 9.1V at 90% 7.3V at 80 5.7V at 75 4.5V at 75 3V at 70 &, 220V on BR2 Placed 24V, 250W halogen bulbs in place of 130V bulbs and gives +/-60V IV rails With extra 1M across R82 op DC goes to 27V With extra 1M across R60 , 0.2V DC on o/p and amp goes into "operate" 2mV over R59 , 0mV over R58 50mV over R61,0 mV over R61 Replaced the leaky BF423 with joggle legged MPSA92 Rails reconnected at "SP" links and main rails are then -125V,+125,61,-61 load test 0.23V , 400Hz in with mid set of vol gives 4.5V ac over 4R Second 2x 1100 amp 19.1V on smps wrt live gnd 54V,-54V,-53,53V on MJ TO3 cans Vaux (5) 42V operate 0V off PIC lines R49 to -13V R13 <>0V R34 <>6V R32 <>4.8V Sometimes will power up with CLIP1 LED on but will not pwer off and 110V on rails R173 goes to -12V R73 goes to 1.2V then 0V Burnt out R146 problems again in a TO92 device in a , gone B-C-E shorted so more obvious a problem. Crest Audio Pulse 2x 1100 op 2 ok , amp 1 comes on clip led on then drops out, no DC on outputs. Burnt 470R R146, oc 56R R139 and TR37 &38 replaced with MPSA42. IC5 broken , o/p on -rail pin 5 i/p -ve at C93 and R158 at 0V Crest Audio Pulse 2x 1100 R229, 100K at IC10-B MT+ no longer divided to non-inv ip; divided -Gref1 to inv ip so no window for the DC error , so falsely tripping, gone oc in effect, due to solder failure, in an area of high capaditance so difficult to find Crest Audio Pulse 2x 1100 fans just momentary flick op 2 goes to negative rail V stays in protect Convinced myself, erroneously, that this time it was a ps or +/-15V lines issue protect lines R10 0 R21 0 R34 0 5V on R32 momentary low V on both + &-15 V lines at opamps (-4V and +9V or so) +/- 40V or so on power Tr devices staying high for some time after protect mode up to 22V on Vaux5 line at D31 3.9K Vaux5 to live gns DVM 18V on ZD8, and R180 for a second but Txdrive for only about 0.1sec Shutdown 5.9V for same time Soft start jumps to 1 /1.5V Zd10 about 0.7V for .1sec R166 to 25V Vref holds at 5.1V for > 1 sec 15V zener over ZD10 stays on longer V on C75 drops from 48V to 20V (beware of this 48V voltage present in working amp long after switch off ) V over R165 24V down to 4V Thermal fuse between opto and R165 is inside the switching Tx 1K across TR47 to keep supply running enough to monitor and 17V pk-pk wrt op gnd, 12uS symmetrical peaks at D50/D55 so both complementary drives working 810R between ZD9 and R180 to disable TR47. Cut the 4 HT and MT "link" points and it was HT loading problem. Removed the 810R and zeroed in again to problems around TR32/33 and TR35/36 overheating. Beware multiple change of orientation etc between ch1 and ch2 and replacing BF422 with twisted leg MPSA42 and BC450 instead of 2SA872 adds more confusion. Added peg spring heatsinks , as per tips files, to these TO92 , requiring reemoving poly cap to grind a slot on one. 70 deg C temps now down to 50 deg C Directly in series R112 and R7 representative of the crazy R numbering are next to the speaker returns on the schematic Protect line data taken again for this particular amp R49 -13.5 to -12.6V R10/R12 -0.03V R34 8.94 to 9.01 R32 4.92V also at diode D51 24.1V to 23.86V 0.083 400Hz in and 1.72V ac over 8R load with mid vol With 2.07R high power load (2.8R plus 8R) , mid vol, .156V 400 Hz in , with both ch powered , 3.4V over 2.07R and 1.4amp mains cuirrent draw Crumar Roadrunner 2, 1979 , Italy, synthesiser Chorus effect not functioning. One of the 5 CA 3094AE not functioning but low level of output. Connected 6.8K between the chorus maximum level signal at one of the CA3094 and other end to the board output. The F 4727 was probably Fairchild 7 stage CMOS counter. ITT SAA1004 f divider. Mostek MK50240N probably = Thompson MK50240 top octave generator. If one key sounds but repeat depression does not then due to mis-alignment of contact spring. Un played the spring must touch the long contact rod common to all the keys to discharge or it will not play when depressed. Crumar Roadracer, RRC, 1978 One note per octave absent. AY-1-5050 Its a frequency divider , 7 stages , broken into a few isolated stages but in this use they are chained together so 1 4024 would do and perhaps 1 + 1/6 4049 for buffering. The trouble is the original uses 2 supplies -15V for outputs buffer supply and -27V for the logic. Buffered trannie input and running the CMOS 'upside down' between 0 and -15V ? Found an exact replacement so didn't bother fudging pinout in D.A.T.A 1982 digital along with AY-1-1320 and AY-1-0212T, MM5891 adjusted pinning may be useable there. Two keys were sticky. Not due to rusty pivot but under each key is a standoff carying a shaped rubber piece to stop keys swaying. Presumably going sticky , replaced each with a piece of 0.19 inch silicone sleeving minus cores. Perhaps squirting talcum powder under each key as maintainence may help. Gain access to underside of key by opening out the metal channel at the rear to release one pair of nibs on the white pivot plastic which allows to slide off the remaining 2 nibs. Slide the key to release from the hidden constraints but still stay captive by the thin and vulnerable switch contact. A nail wire staple hammered into the casing to keep the top switch plate away from the leftmost key. Custom Sound 2005, Mosfet amp, made 1988 Volume faded down after about 1/2 hour . No tranny/diode thermal monitoring of the heatsink and no FET for gain control in the pa or FET in the preamp , all 4558 opamps. No obvious over-heating or solder problems on any of the boards or flaky gain pots. Springline reverb throughput had failed due to corrosion on one of the springline phono connectors. This Accutronics springline was 200 ohm for in and out pickups. Dummy loaded (4 ohm and 6V ac) took the heatsink up to 70 degrees C and held that power level for 40 minutes with little variation in preamp output, pa o/p or DC rails so a matter of the usual treatments for the numerous IDC interconnects, sprung IC sockets and 1/4 inputs, despite no response to twizzle stick and reported fade. Dealt with all interconnects (stagger-marginally-bent the pins and cleaned to give better holding), IC /IC sockets and beefed up all 1/4 socket connections as 5 channel all in a row, by running silicone rubber cord the length over the sockets with Hama/Perler/Pearler beads 2 over each contact, fed onto pired up cord as in threading a sewing needle. Pairs of holes drilled through the pcb to take wire loops and a Hama on each to tension down the cord between each socket. Then hot-melt at the ends the down-pulls and the twisted ends of the wired tensioners. The mains fuse cap was exposed to a screwdriver so replaced. 2x 2SJ50 and 2x 2SK135 bf470, 2x BF469,2x BF423, 1K, 2x 1K, 7x 4558 on preamp Custom Sound Colt 10 combo amp Intermitent o/p like a bad i/p socket. Dry joint on resistor at i/p. Another dozen or so leads had holes on one side of the solder joint. It looked as though the lead cutter plate after assembly was blunt and pushed all leads over before cutting and it had taken 10 years for this stressing to open up as dry joints. David Eden "The Metro" Bass Amp,600W , 2000, 50 Kg Cut out in use then came back. Next time of use, failed to give output but owner noticed clip light in pre-amp functioned as normal Now I have it, I cannot induce it to fail. Likely suspects the discrete wire IDC connectors for power and signal interconnects, unsupported wire-wounds on end, mains thermal switch. I did not like the front panel switch in line with the speaker line. In standby instead of cutting/shorting the main amp input you switch out the speaker. IDC interconnects on the speaker lines and power lines seem a bit irregular to me but as cut out rather than distortion those power lines presumably ok. Speaker units check out ok. The function of the 12V, 10 W "festoon " bulb in the variable crossover in the cab is a fuse. Speaker switch rated 3amp and thats for AC, could easily be the problem, let alone potentially "fatal" to the amp. The cab wiring and pair of 4 ohm speakers in series seem fine. It would not take much fumbling in poor light, drunkeness, confussion or whatever to flip that switch in full use , its not recessed and in the back of the cab. The other 2 paralleled outlets are not switched, but I may hardwire/solder back to the pa. Found another nasty under the ps board but don't think it is the main problem. This pair of wires to the speaker switch had one of the wires squashed between a large W/W ceramic cased dropper under the ps and the chassis. Cut some high temperature silicone cable sheathing into a spiral, wrapped around the replacement wires and put cable ties to each end to. Original wires melted through but as it cuts the earth to the speaker, presumably no problem as such and wire not broken, just failure to sometimes switch out the speaker. But there is smoke blackening or something grimy in that area but it could be a small electrolytic parallel to the fan cooked as it is directly over the large droppers and leaked electrolyte but all rather nasty. The aluminium of the chassis directly under this particular dropper has a strange flecked grey corrosion or something that probably more likely due to electrolyte rather than vapours off the charred PVC insulation. The corrosion i've photoed here The overexposed T area is the mains transformer and the groove marked "<" was created by the squashed/trapped cable or exposed wire core probably vibrating. From "<" to T only about 10mm so just 5 mm or so free gap to run these 2 speaker wires between mains torroid and high temp wire-wound dropper with no added high temperature sleeving. The grey flecking is what I'm assuming is electrolyte corrosion effect rather than burnt PVC product. If this fan lytic over the fan supply dropper leaked to short in use then dropper would generate more heat as well so compounding as well as shorting out the fan to the main amp heatsink. The owner had used the speaker switch in the past, during sound checks. The protection circuit is activating before the 60 degree centigrade fan switch is cutting in, under high load. The fan switch temperature , testing in isolation , is about right. The big triac on the mains, crowbar operation to blow the mains fuse if too much mains power drawn presumably, 60K to neon for UK and about 22 ohm in line between triac and switch. I've photoed the tracks and components and determined the schematic of this power amp. Hard-wired the 2 lines from amp to speaker outlet , there were 12 chances of a break in that route, to and return. 3 pairs of IDC and pin connections in each line. Using dummy load the thermal protection circuit was activating before the fan thermal switch. Monitoring the line from pa to ps with the LED thats on if all is well. The voltage changes as heat builds up from about -13.5V down to about 12.7V when it switches to about -0.3V , LED goes out and pa is killed. It was the LED on the ps that was failing. This LED passes current to the start-up hold-off circuit as well as turning off PA if the fan voltage fails genuinly or falsely. This LED also on over the high power droppers, replaced this LED off the board as well. If I'd thoutght about it I would have added a second board off the ps , bolted to the chassis with these 2 offending high power droppers on it away from the ps board. Bad design slinging them under the ps with active components over (heat rises). Added a 40 degree C switch in parallel to the existing Asahi US-602S , 60 C one but resets at about 25 degrees C. If one switch fails there is still the other. Replaced the MPS8599 with a BC212 rotated 180 degrees to pin match , in case the original was suspoect due to excessive heating if the fan had been stopped. Before pushing into the heatsink, check temperature controlled function of reducing gain to zero by a metal funnel leakily connected to a low setting of hot air gun and piece of heatshrink tubing on the small end of funnel. ps main voltages +/-78V dc. fan supply w/w dropper 75 R , 100R for preamp pa uses 10K, 2.7K, 3.9K, 4.7, .39, 150R 2SC3858, 2SA1643, 2SA1494, 2SC4327, MPSA43, MPSA92, J112A, MPS8599 Heat output measurements on 400Hz continuous sine i/p. Into 4 ohm load with room temp 19 degrees C, for 25W o/p in load, fan outlet temp 25 degree C for 52W , 30 degree C at fan outlet David Eden WT800, 2010. Blows mains fuse an hour into a set. Then over the weeks blew replacements every now and then. Blown ones not retasined but owner reported they were black stained. Sometimes after 1.5 hours originally , now sometimes soon after switch on , sometimes a bit later. Amp plate says 5A(T) for 240V use. Inside the IEC, is one non-blown 2A(T) in the active position, ah! the simplest of repair jobs, BUT No reported noises like magnetisation buzz or speaker noises , no smoke or smells. Owner uses the same cab and speaker wire with another amp ok. No blown fuses retained by the owner but reported to be blackened. 2A fuses passing 3A or so and then failing when asked to pass 4A say, but they will have fuse-wire breaks , not vaporisation and blackening. Tx torroid 0.8R or so per primary , measured cold, seems reasonable for 135mm diameter, 65mm high Tx. Not in a position to check the main caps yet , but no bulges. Any Eden usual suspects? PbF and RoHS stickers a-plenty As found , a 2 amp fuse in there in good condition , not blown because the triac Q6025 has failed, so front lamp for live mains but does not turn on via the switch googling alternistor "600 volt" throws up no UK suppliers for 600V alternistors luckily no one ever uses a snubber in this use, usually just a triac, so replaced with an ordinary 600V triac and turns on and off ok, presumably maker had a stock of alternistors , so used them instead of a triac there Digikey seemed to list alternistors but not 600V ones. The failed one has no T1-gate resistance in the 10s to low hundreds of ohms, is that a (sometimes) characteristic of alternistors ? otherwise no gas venting through the epoxy fill or other signs of distress 800 watt toroidal transformer operating at say 400 watts. Secondaries lead to conventional bridge rectifier and smoothing caps for +/- rails. A break appears in the DC rails central 0V return to the transformer, could that lead to a blown mains fuse, via inductive action? The power amps always survive . In the process of exploring suspect caps etc and turning over the pcb, the spade-connector for this 0V connection came off the pcb spade. Looking under x30 on the spade and what I can see of the line spade-socket, I can see no sputtering or smoke trails or anything suggestive of a problem there. I'm aware that a valve output matching transformer working hard and there is a break in the speaker wire/connection /voice coil then enough voltage can be induced in the primary side to knock out the output valves and weld turns on the primary. But I do not know if similar in a mains transformer would give enough current , from the energy stored in the inductance , to throw back enough current , at over the mains voltage , to knock out the mains fuse. This amp has an inrush limiter, the heatshrink over it looks fine. I don't know if a VDR variant or what but if it is the usual NTC thermistor then its cold resistance of 0.6 ohms looks suspiciously low. I'll have to strip off the heatshrink and try and find some numbers and data for it Inrush limiter marked with logo something like 8 in a half circle VEI or UEI , 20SP, 0R7 Having difficulty finding data on this but cold 0R7 agrees. In 240V land I usually find inrush limiters of cold value about 3 ohms. I'm wondering if as its a USA made amp then these limiters are used for all models and its not really high enough cold value for reliable 240V use. I'm thinking of odd magnetic domains building up in the core of torroids and occassionally reinforcing the inrush combined with an initially only marginal rating for 240V use. marked 20SP UEI, looking like VEI looks as though its N20SP007 on looks too low a value of cold resistance for all eventualities 240V inrush current use Its a bit much to see that UEI logo of an egg cup with a variant of the ON symbol inside instead of an egg, as the poor legibility 8 in a half circle here, on a roughish surface, but I'll accept it as so. 6 amp rating for the international model, internal wiring set for USA is the correct component, for UK 3 amp is fine but I suspect the cold 0R7 is just too low. I'll replace with a higher initial ohmage NTC, 6 ohm cold, 2 in parallel for the current rating. Tx .8/.8R / 1.8R 135mm diam,x63mm Removed the physical left hand amp , leave earth bond bolt in place Earth wire crimp for the DI board fell out also Replace 1 each , speakon screws so you cannot hot test with the rear plates touching the solder points Marked 10,000uF , 100V caps 1 to 6 To remove the caps, start with hot air gun under one set of 3 to break glue bonds and solder as double sided wide traces also. Then use 100W soldering iron to remove those 3 and the other 3 then just need the 100W. Obvious weeping of electrolyte under 5 of the 6 caps, 1 had a couple of drops, but no sign of leakage onto the pcb, but assumed at least one cap has failed at high temp and self-healed Blackened pcb under R10 and R11 discoloured bands but reading 3R3 each ,pcb charring >30M DVM probing and goes from 20V Tx secondary to 1000uF 10V cap so unlikely a mains fuse KO Anodes of the valve go via ok MPSA92 to the ps , but may replace the 2x 160V 10uF caps in that area. Just leaves the 2x paralleled 3 , main caps 100V 10000uF. Other than separating and heating and measuring ESR (not necessarily related to self-curing internal flash-over) , nothing else left to explore? If its recovering interlayer discharge inside the Tx then can't do anything about that, any sort of tell-tale for that scenario? presumably add fuses would 10 amp blow before the 5A mains fuse with failing electro?) to the power rail secondaries Heavy engineering job as a solid block of snap-in 6 Jamicon , 85 deg C, LS, 809K(M) 100V 10,000uF. Presumably failing because the contact verticals between are filled with filled silicone rubber and hotmelt glue in the 2 central gaps and 85 deg C ratings. someone's internal view of similar amp 12 1500W hot air gun to break the solder and binding of the most amenable set of Cs for wedges under then completed with a 100W soldering iron : 4oz board , wide traces and both sides of the pcb. No oily messes on the pcb but only one cap end is dry, 4 have an oily film and one has that plus drops. Expensive set of replacement 105deg C ones plus try and get some through ventilation, perhaps the replacements set at an angle to form a sort of duct and a small fan or as in line with the amp fan perhaps a duct only . And hope not an on-going internal Tx problem Cold ESR of each is good and warmed to whatever a minute of low setting hot air gun gets them to , no noticeable ESR change. I suppose the only test would be a current limited 100V supply , resistor and voltmeter to monitor implied leakage current and heating each cap . Cooked all 6 at 85 deg C, with thermometer in the middle of the block, for at least 30min and then applied 110 volt DC to each in turn, all charged up and held for 30 seconds or so and discharged normally and equally, while still at 85 deg C. But not too pleasant electrolyte smell in the room. Orientation of the caps was up the other way from useage and no vibration. I wanted one to show some obvious problem. Removing ps board , remember the 2x voltage regulator screws R10 and R11 are in fan control , overhearted to loss of band colours, measure 3.3R each, slung one replacement undedr the pcb. Blacking of associated pcb material , >30M DVM-R PA p/n 10150, rev C 3x A1492,3x C3856, TIP42C ,TIP41C, KSE350, KSE340 6x .45R 5W, 2x 75W 2x 68R,2x10R soldered th sw N/C spade terminalsed th sw N/O N/O one thermal switch was KSD301 K050 PN so 50 deg C to switch on fan, logo lightning stroke in brackets Both 10A speaker fuses ok VRs 7815A & 7915A ok valve anode pins connected 1 &6, line to Q1 MPSA42 R5 390K to orange wire of P3 and J3 to C10 10uF,160V on ps Beware with no PA connected HV retained on the 10000uF caps for a long time Grubby patch of blank pcb material under top cover is a fudge to avoid something on the top pushing down to cause a magnetic short to the Tx coachbolt. The mark is just from physical touching of the thread, not from electrical discharge. Removed coach bolt and no nasty smells or black streaks inside the Tx cavity. also no awkward smells inside the amp , on first opening. Unlikely repeated mains fuse failure, but both PAs stay functioning , due to internal problem in the Tx but could be a first, always found to have welded shorted turns rather than intermittant shorts. After removing main caps, clean and straighten the "snap-in" offsets of the pins. Ball mill back rings around the 0V pcb traces top and bottom. Cut some 3mm thick paxolin to glue over this central area to give a cant to the caps when replaced. The 63V, 2200uF cap nearest them needs desoldering and canting over as well to clear one of the big caps when it is canted over P2, single wire to physical LH amp only . RH amp at the ps has on its conn a trace of insulation for the corresponding wire but no wire. Fully tighten Tx only after refitting RH amp as only just enough clearance space. 2 pieces of nylon cable ties pushed into the gripper tangs of the mains sw. Triac gate has 4mm tag/spade. Replaced triac with ST make BTA40-600BC, no change to 22R etc required Refixing amps,fit the isolated single pillar first and then the 2 h/s sc. Tried out 1 pair of main caps only resoldered in , initially Green front LED on and red ps LED on +/-76V on main rails for full mains V 101V ac on thin red/orange lead T13 , 20V Y wrt Gn T12 20V ,T11 Because of the nasty rats nest of wiring between fan (blows inward) and the ps caps decided the only option was t add a small fan in the only bit of available chassis space, near the valve and L amp. Pilot hole and then 1.5 inch Qmax hole cut and 2 mounting holes and some expanded mesh cover and a couple of washers to add space between mesh and active part of the small fan. Removed those 2 caps and refixed all 6 with 6x 20mm fuse holders fitted under to 0V also 1 1.6A fuse in the 100V wire , heatshrinked over and 1 x 3A in each 20V wire. Hopefully will indicate which cap is failing , if continues to do so , even when running cooler, at least should not knock out the mains fuse, just some hum or distortion from 3+2 main caps DC at main ps conns from J1 to J4 J3 J2 , no fan on -76,-13.8,0,0,0,76,?,0,0 -13,0,0,0,0,0 -15,15,?,135,0,0 -76,-11.5,0,0,0,76,00,0 134V and 135.5 V over R7 DEcided vibration , plus the overheating caps may have contributed to internal cap shorting Looks as though the 4x sticky pads had been removed from under the chassis. Added tap washers , 1 under each of the most appropriate sc under the chassis. With a ball mill ground out a recess to seat the head of the existing sc without protrusion. Usual UNF/UNC / UK problem, just about could use the existing sc if the captive star washer was removed. Cremmel and .5mm disc to grind a slot in the washer (and a bit of the head and shank thread but ok) to break off the star. If cable bunches are set between caps and Tx then perhaps no ned for an extra fan. If no valve in place then a mysterious deep rumble /rustle like wind noise Dunlop Cry Baby GCB 95 Owner lost the original broken switch and of course did not note the wiring. Deduced wiring on DPDT switch Blue / Blue wire to pot Purple / Green (commons) o link o Needs a long stem footswitch. With this one with what looked like the original felt pad , 11.5mm between top of sw button and top on internal back nut eg Alpha L , 8D1 is too short. Never mount one of these footswitches without the rear backnut as any force bearing on the flat body of the switch will break the weak brass nibs between the two parts. If too short , glue a 3/4 inch diam, 1/4 inch thick tap washer to the original felt pad and take up on the back nut. As a rough gauge to correct posistioning. To change switch state requires both hands around the unit to compress the pad + sw. Roughly equaivsalent to deliberate but not excessive foot pressure. Dunlop Cry Baby GCB 95 ,wah wah,2005 From a wah-wah pedal only 2 years old so I don't see the point of replacing with more of the same, as these symptoms are very common. Poor bypass function and now total failure to switch between on and off Both 1.8mm x (11 down to 10mm swaged )stainless steel rivets ground off to separate the halves,push-push latching switch Unless anyone knows differently then I suspect the poor bypass contact is due to the interior packed with non-conductive grease. Carling, Mexico is the make of this one , single pole c/o, silver plated contacts and dumb-bell that can just about be seen in the centre of the top image,then a locating cup, then compression spring, then brass cup that seats the end of the swinging arm marked L in the next images. The dumbbell jumps the 2 contacts at the top of the image and runs along the continuous lower one, enlarged in 4th image, 5th is the swing arm magnified. some background on Carling switches Featured Article :: A comparison of boost pedals :: by Ken Nossardi I think I agree with the comment in the quote about machine tool wear. I've not removed the rivet that holds the ratchet mechanism - maybe shown on a patent site somewhere. I suspect that ratchet mechanism, produced by worn dies, is just enough to bring that swing lever over to just over half-way when tested off the production line. With, now, no reserve for in-use wear. Cleaned the silicone grease out as not used for mains switching here, otherwise 1A 250V / 3A 125V rating. Why silver plating and then non-conductive grease in low current/ low voltage use ? There must be a "ball point pen" type latch action in the bush part so the down action pushes the L arm one way then the other on the next down stroke, with a click of its action on each upstroke. plenty of spring in the ompression spring between dumbell and brass cup, so no lack of contact closure pressure , leading to the bypass problem Presumably due to wear the underside of the button eventually bottoms against the end of the threaded part marked V, when L is only half way across. It needs to go a bit further than half for L to swing across, via the dumbell/cup spring sub-component action , to the other side. Slightly tightened a small Jubilee clip around the threaded bush, as a guide, and hacksawed off about 2mm at the V position, not apparent in these images, so can be quite neat. Stuffed more plain silicone grease in the ratchet section No matter, in this case (not mains use), may replace the rivets with Spanish windlass "E string" wire over 2 small soldertag rings and locked in place. Anyone know of a source of such small diameter /long rivets for other occassions? Of course just fixing the lack of switching does not require removing the rivets. In the end just used 2 small eyelets in the metal to locate under the back nut , 2 cable ties around and one across to remake. If there is non-conductive grease in other , otherwise 240V rated switches, then that could be a generic problem with all switch makes, used for low V, low A purposes. Missing feet requires UNC screw. Missing battery cover see tips files. Dynacord Powermate 600 mixer amp , 2006 Supposed to have only a minor problem for repair but there is obviously (also) a totally black shapeless lump , presumably remnants of a burnt out capacitor. Marked C17 between F1 and F2 low power rail AC fuses. Anyone know its value? probably about 1nF, too low a voltage rating? or because it lies over a power rail track between D17 and C7, coating burnt off. Loads of these mustard yellow globular Cs around the board The output relays seem to present a short to the speakers in powered off mode, have not got to the solder side of the board yet to explore. RoHS construction, of course may present other nasties when I get there, not originally forseen. The muting TO92 J111 FET is falsely pulling down the signal line, -18V control V on gate dropper of both channels but not so the gates. Not the FET but the gate to ground cap going ohmic, see more relevant exporation on one of my tips files and item on WEEE/RoHS/PbF Mono operation secretly selected rather than stereo/2 channel operation. ? Both channel signals get to the mixer output jacks and the mixer ribbon is remade with both channel lines intact but there is a break in one throughput before the ribbon, but punch-in 1/4 socket bypass contacts are ok. I was being mislead by L & R on the overlay near the mixer/PA umbilical ribbon CN1. L is the L ch and R is the quasi ground for the L ch, the R ch comes in nowhere near it. Full signal L and R gets to the PA but only very low level gets to the R ch PA pre-driver stage, in for some messy opampish fault finding or false mute, if the power rails are ok. I've not seem them before, no name on the exposed parts of the connector. 0.1 inch pitch ribbon maker ?. views of connectors , same, both ends of the ribbon for photoing convenience. top as found, pcb part, ribbon part internals Black end pieces are just locators and for polarising,different sizes/recesses, not gripping the white bits. Locking is done internally somehow. Anyone know the professional way of unmaking these connectors? you do not umake the second IDC connection, per pin, in the process of separating. I ended up using a knife blade and then jeweller's screwdriver to get purchase between pcb and white part that goes down to pcb level, lacquer damage can be seen in middle view. A dentists sickle probe as a lever into the small holes along the white part edge levers it off. 4x MJ15004G, 4x MJ15003G 4x 4r7, 4x .22R, MJ15031G, C4793, MJ15030G MJE350G,MJE340G, BD241B, 2x LM317J, LM340T5 1K CN18, to CN8 ,55R CNS1 has +/- 15V, 24,51 F1 , F2, 40V ac +/-69V dc rails L bias signal ok fan blows outwards Rch mute, J111 Q303 preceeding opamp OP301A pin 1 L ch, J11, Q103, opamp 101B, pin 7 LM317 +16, -25 The J111 , falsely mute reads -18V, -1.1V and proper operation -18V, -17.6V 0.1uF/100V MLCC gone ohmic. Putting a DVM/ohms over this showed wavering 20K to 30K , same when removed. .125V 400Hz, 40dB gain, 0db slider ch1, 0db on master 0db on bar meter, 0.8V on l/r trace at CN1 main board 1/4 in jack in Main Output , L 0 ohm to L at CN1 Ribbon (L) 9 to mixer out 10(R) CN(4) sig (L) H1 SIL pin 4 CN(9) Sig (R) pin 2 of SIL H3 Saw the owner 6 months later and no further problem caps or at least enough to cause noticeable problem. Dynamix Stage 250 (plus suffix ?), 1984 mixer amp Intermittant loss of one "tape" input channel Retaining bolts hidden under the feet. There are switches at the phono inputs and replaced them with unswitched ones. Uses 10R 10p16 , 10N16 4560D, 7915, 7815 springline 75R, 40R +/- 64V Intermittant drop out or relay and loss of o/p Bad umbilical IDC connection on the relay board branch off. Moulded or invisible closure of the black IDC sockets. Ball milled alternate sides , cut into with scalpel and thin nose to bare wire and IDC blade, flux and soldered. All 6 connections of the last 2 connectors. Failure of a + or - 15V to one of the prea channels would just mean loss of one ch not total amp loss of o/p. Did not cure the problem , cut out IDC and header, soldered the wires to the pcb. Cause unknown as opened up the socket and plenty of spring on the contacts and continuity of solder over idc seemed fine. Makers probly did same on one of the signal IDC connectors , soldering to the header As on a board where the pots did not match separation spacing on the front panel , replacement ones would not have different spacing. the 100uF is not the relay timed off timing cap the 2 V reg h/s were too close together, bend back vanes Only half the relay used for o/p line, green flash and bang in speaker so heavy DC . pa checked out ok, due to bad crimp connection on -ve side of main bridge rect. Also bad crimps on IUC and mains fuseway. Another time intermittant loss of o/p FX level pot ground bad. On relay board 100uF is not a timed off cap. Black .1 inch Harwin type IDC connectors are bad contact somewhere. Makers had done away with one at manufacture, soldering to the header pins. As front panel spacing does not match the underlying board , and splurged pots pins then a bodge job at making. Soldered the first 2 ribbon connectors to the boards as loss of power rails there leads to relay dropping out. Problems on the others would just lead to loss of one ch. Only one set of contacts used on the relay. Excessive green flash on contacts at dropping out due to bad crimp terminals on one of the main DC lines. Bad crimp contacts on IEC and fuseway. 7R NTC on mains line Electro Voice M/C 150 microphone Dead mike.Broken wire at the switch.To access unscrew the dome,desolder the wires to the active part. Remove XLR housing and then the 2 screws holding the switch to the body. Came bouncing back a few months later. It was now obvious the problem with these is the transverse pin bends. If the gust is held in place while the end of the pin is ground off and extracted and a replacement one made , then that would be the solution. Electrovoice EV Sx 300 dropped and measured 25R , soft tap on side and down to 13R Dart point in spades to remove mark leeads before removing but worst ones were to the speakons bass 4.3R, horn 4.8R to remove horn , remove 2x 5 recessed bolts on rear and 2x2 seemingly "blocked" off ones, removed from the front main coil 0.9R, other one 0.6R polyswitch X050 1.15uF, 160V ac 10R 20W removed speakon spades and soldered in [place and restresses other spades 5.2R overall at input Electro Voice Sx 300 speaker Bass driver giving off a noise like frying bacon of fairly constant level compared to varying audio level. They had used epoxy glue and soft contact glue at 2 different stages of fixing the spider to the frame. Epoxy had squeeged into the interior forming beads of solid epoxy up to about 10 mm long by about 2mm that had later broken off and was rattling inside. So gummy/soft glues only is the lesson . As there is always bits of sub-mm aluminium oxide etc , but greater than air filter mesh size , inside speakers, that don't seem to make any humanly observed rattling interference noises , anyone any idea what is the size that becomes intrusive ?. In the core that is , not staples etc on the outside. RoHS stickers all over and all sorts of other problems in the cab but not PbF isssues (this year) These bits were rattling around in the interior space not passing through the air filter gauze or getting graunched in the vc gap. Demounted spicer and cone and for "reconing" this one I used 3 slivers of credit card, hardly thou/mil sorts of dimensions. You need a jam fit, to coin a term. Not a clearance or sliding fit as you need the cone to stay at a pushed in distance, say 5mm below natural level. To allow the glue to have a closing pressure that is a once only application of force. Not removing hands and then placing a weight inside the cone. So the circular VC former goes slightly triangular with 3 credit card slivers or slightly squared with 4 (excessive deformation/ holding force for this one) The precision required for a shim cylinder (even with an axial gap) for coning/reconing would be near impossible to have a "jam fit" This one given a work out with high power 50 hz and now back with the owner. Does not bode well with its fellow, 5 problems with this one. Loose horn, loose spade connector, another one the wire came out of the "crimp" on normal handling, spider of the bass unit partially unglued from basket and these bits of black epoxy rattling around inside (now in my black museum) Removed epoxy coatings with dremmel and grind disc, also abraided the spider laquer covering for better key to contact adhesive. Cut into periphery of dome for jam fit spacers. Before realising had to remove cone and spider- thinking just regluing the free part of the spider and clearing out loose epoxy. Cut a piec of hot melt glue stick , knotched at the ends to lodge on dome remnant then dowel with a large grommet at each end over the speaker mounting rim and rubber cord between the 2 rods to pull the cone away leaving inspection and gluing gap at the spider. Ev bass 812328306293 Ev horn DH3 8033099006296m Horn loose rear and internal screws , use cutdown ratchet spanner and hex bit to undo if not taking the 2 halves of the cab apart or slackened a bit. Wire to horn dropped out of a crimp on moving the wire Part remove cabinet screws on top half to allow removing horn. Remove rear screw before parting the cab halves. Intermittant speakon spade connector 2 unmarked festoon lamps under crossover pcb , powering from 3V and 1amp , after 1 sec glowed orange .5R cold and 1.1R across xover to T Elka organ /AY1-5051 replacement From usenet discussion, placed here for clarity AY1-5051 Fixed Modulus Divider chip? It was made by General Instruments (later Arizona Microchip) and is a PMOS technology. a couple of salvaged 1978 , AY1 5050 in front of me with pinning, no knowledge if working order. With a DVM diode test and -ve to ground pin one measures .71 to Vgg and .66 to Vdd pin other is .8 and .74V for isolated dividers with no internal linking and a few readings referred to pin 1 as -ve to pin labelled input .88 and its o/p .78 and some others .95 i/p and .86 o/p ,97 and .85V o/p those with internal linking are nearer the o/p readings, up and down + probe to pin 1 ground then no forward drop reading to any other pin , max 2V IIRC on Fluke 77 Early Maplin in UK catalogues had pinning etc for a number of AY1- organ use series Tackling a functional replacement Wire a chopped down to 10 pin turned pin socket to the pcb and glue in place. Another chopped down socket , to plug into the first, wired to a piece of matrix board. Try an "upside down" ,positive ground (is that possible?) CMOS divider between Vdd and ground and voltage divided input signal to one of the CMOS inputs and and try just one output , level shifted with transistor and a couple of Rs , from Vgg, to drive any high level tone generators or whatever comes after. Power supply. You have to use the -27 volt VGG since VDD can be modulated. So a 12 volt or thereabouts zener, and a series resistor should be ok to get a -12 volt supply. Which will feed some CD4000 family chips, running upside down. Their positive power supply being the PMOS ground. Typical drain for the old chip is 3 milliamps, that should be plenty for a handful of CMOS logic running at audio frequencies. For each input, an input resistor, diode clamps to the CMOS power positive (gnd) and negative supply, and a schmitt trigger buffer or inverter. CD40106? Then use either D latches (4013) or JK ff's (4027) for the dividers. Easier to get the short divider chains than the CD4024 if you don't know how the external circuit is wired. If which edge is the trigger matters, you may needed to chain one of the spare 40106 inverters to get the right polarity to feed the flip flop. For each output, a small p channel MOSFET, source to (PMOS) ground, with a 6.2k ohm drain resistor to VDD. (Or maybe a jellybean PNP with a base resistor. Depends on the sound that results, perhaps). You might need a capacitor or RC filter across the output to slow down the edges.- Mark Zenier E-MU 1616 digital audio system Failed 48V ,.375A smps , TE18 on pcb ADC0000003610 Only 6.8V output 1206 footprint inside a Chinese in-line smps. Amber colour showing an underlying zigzag track like pcb trace inductor and a tiny fuzzy bit. In series with 15K , only, and going between the coldside pre-rectifier hf ac and the 48V dc output . Does not measure 0 ohm, not a fuse in that situation. Overlay marked ED201 , ED = electrostatic discharge? Note, its on the cold side. "surface mount" "spark gap" in goomages threw up nothing Bad solder joint on the v reg should be the problem but just wanted to check what this new-to-me device might be. Case cracked open in a vice painlessly, 2 clasps at lead ends. looking under x30 it has a gold coloured if not gold plated surface with a bit of ptrofiling, perhaps hiding another surface under as seems continuous metalling from land to land, with a tiny brown dot in the middle and clear plastic cover over What a plonker. Now it is knocking out 48V DC, its function is obvious. It would have been much more obvious if it was not at the edge of the board with the L missing off the overlay designation ED201, and a more obvious window in the casing. I did discover that there are such things as SM gas discharge tubes/arresters Lid is "bottom" and undo both TO220 bolts to release pcb ( broke a trace at the driver tr before realising the fixings issue) Hotside C3866, 1.6A fuse, thermistor 1R, 150R, 1M,120K peke diode, 33K AZ431 AZ AE1, TO92 shunt reg failed , is it higher rating than all the other 431 datasheets show? 15K,220.150K Replaced .47uF ,50V as 75R ESR Replaced with a TL431 and ps worked but there was 44V over the regulator, max 40V in all the data I saw. 44V.0,2.5V wrt poer 0V 2.5V on either end of 220R 18K to 48V 150K//975R= 968.7 Measuring DC over opto , R and op for no load 1.11V,3.1V,47.6 500R load 1.02,1.41,47.3V 220R load 1.04, 1.09,47.1V so functioning but as the original had failed I have to assume because more than 40V, failed at switch on. Eventually settled on adding 330K to the 18K and adding 1.8K to 1K to give 2.8K in line with the opto giving an output of 45.2V no load 9.63V over 2.8K 4.41V with 500R load External unit , unconnected to pc, Red "48V" LED and blue LED on , other LEDs show random display including clip LED ,but normal. Just power-off click on phones monitoring Owner does not use phantom , probably ok , but works ok with now less stress ovver the regulator. Engl E320, Thunder 50 reverb, 2002 "static" rustle valve amp Celestion V12-80 6.6R reverb tank 1.1R, 220 tr 11 R, Bk 0.1, rd 37.9, gn 1.1, olive-r-olive 1.8-1.8 2 broken spring washers on the 3 pa bolts (windy drill toequing ?) Remove 4 large bolts on o/p tr cover to release tr. Remove 4 prea standoffs from chassis side. Hold rear panel cover plate in with a looose 1/4 inch socket Beware of flying LED and straining the grey ribbon flex solder ends so cracking. Fix a bracket to the chassis captive nut for a vertical length of dexion and a strut from that to the other chassis end captive nut to create a vertical support frame for all the internal pcbs , to work on. Leave the bridging yellow and black wires and ribbons in place. Angle to give clearance between 5881s and dexion. Some long component leads not cropped Even the maker's ECC83 retainers are an awkward bodge-up, not even fully screening. Place retainers over the valve pip then spring the tangs into the chassis slots Owner has managed to get away with dragons teeth retaining clips digging into the glass envelope of his replacement type with no bakelite base . How to fabricate something approximating those woven glass mesh baskets that go over the envelope and then a pair of springs down to the chassis or any other ideas other than replacing with based envelope types ? Incidently the first thing I did was undo the screws of the dragons teeth in hope of relieving some of the teeth force before removing the valves , but was that the correct approach? I don't fancy making a pierced metal dome shape, that has to avoid the fragile central area of the glass dome. So far I'm thinking of a length of high temp glass sleeving knotted into a ring, slightly smaller than envelope circumference, with a balancing "knot" on the other side. Then silicone sleeving or springs and glass sleeving down to a pair of solder tags as anchors. Nasty dragons teeth chips in the bottles but they survived. Made up PTFE "jockstrap" as retainers, see tips files. Another awkwardness of the Marshall ones is the tension points must be a good inch below the bottle tops and part wrap around to avoid sliding off. Yes underslung 2002 German Engl E320 50W combo. First time I've come across one of these , to do anything you have to take the whole amp to bits. Bad centring between RCC valve sockets and the holes thru chassis Epiphone Triggerman 100H : see Grainger Euphonic Audio,amp 350,2001 Presumably a stock fault with these Euphonic Audio, USA amps. If a problem not relating to the ribbon cables , before doing anything, beef up the soldered ends of the ribbons with hot melt glue or the ends will fail from brittleness. I'm having to replace all 8 of the 1/4 inch jack sockets. 4 of the 8 are totally breaking up inside. Assembly flaw - they used unreinforced plastic spacer rings on the bush inside the chassis, not dense fibre washers. The ring breaks and the bits drop away and owner tightens up the front nut, not realising that without the spacer then the socket is skewed/levered against the pcb and rear of front panel and the socket housing starts cracking up. Otherwise sturdy but now detrimental soldering of the pins does not allow any give there. The pins are joggle-formed to tightly fit double-belled eyelets and soldered through the board so as solid as can be, with base of socket tight to the pcb. It seemed odd to see a 555 in there for just a hold-off timer function. You need the same Ct/Rt values in both cases and one does not use a 555 The other pig with this amp , it uses that grey ribbon with soldered stranded wire cores that can only take a limited number of bends/unbends at the terminations before cracking. 4.7R, 38.2K,15R large Rs, NE555 2x 10N20, 2x 10P20 4x 0.1R, thermistor 2.7K in circuit cold Transformer internal fuse 130 deg C 3.7R//gn 1.7R 16.2V, Y 0.9R 14V, or-or 0.6R 110V LM393N Prea LM79L15, 78M15 9x 2072C, 3x 072C Ribbons Send / Return - 1?,2?, 3 gnd, ret line i/p -13V supply phones/tuner (maybe) -15V, Tu, G,G, o/p,+15V, phones Event EZbus digital mixer not booting , LCD message says: "becoming EZbus..." Dead as all functions controlled digitally, except for the display showing initial message. This is someone else's broken one, posted out there and no response "The power turns on and the green LED's next to the System and Audio buttons flash for a second and then the LCD displays "becoming EZbus... It does not advance from there. " x5 visual inspection over the main board shows nothing amiss. DC rail voltages agree with the regulator types, reseated cable connectors. No battery or F-cap found unless on the analogue board. Start up is the same as that other one , I'd not noticed the 2 LEDs flashing on for 1 second. Changed 3 , 0.47uF caps of ESR 25 to 30R but system still hangs. Beyond checking oscillation around each of the 3 crystals its then a matter of seeing if there are data sheets for the main chips I've downloaded the datasheets for the controller, Cypress AN2131QC, and 24 Bit Audio DIgital Signal Processor, Motorola XCB56362PV100 so another download for the CPLD XC95144XL, nowhere near any crystal leaving converter CS8420 and flash mem AT29C256 of the big chips I did try powering up pressing System + Audio (the LED flash up pair) while powering up , but no change But I will try Play+Record mentioned as another make of digital mixer reset before delving more into the hardware. Any other button combination suggestions, nothing for EZbus found out there. As nearly fully separated 3 lines of 28 control buttons I will try the small subset of 378 combinations of adjascent pairs and the subset of adjascent triplets of 3276, 3 button press combinations at power up, unfortunately having to leave 10 seconds in between as longish 5s or so power-down/clear. Then monitor the 3 clock lines to the CPLD and then try forcing the GSR (Global Set Reset) pin This other person's experience "When connected to a PC computer via USB, the computer recognizes that a USB device is found but cannot install it because it does not recognize what it is. I went to the Event support site and downloaded the EZbusInstaller, Firmware, ASIO update and XP update. Followed instructions to install the Installer and that seemed to work, but when I try to run the Firmware it does not recognize the unit and gets and error message that says no EZbus connected. The Firmware instructions say that in order to run the file, the unit has to be set so that the display is at the USB setting, by pressing the System button and then the Next button several times. But it won't pass the message that shows "becoming EZbus..." " suggests that and this is a "pre-POST" problem but there is some variation in LEDs lit on some button press combinations at power up , sometimes the MIX LED lights on one pair of button presses , rather than the System+Audio LEDs, as normal. Does this suggest a post-POST problem? unlike from the EZbus FAQ having presumably gone past that and then hanging at a blank screen but is initialising the USB function there. " symptom: I tried to update my EZbus firmware and, and now my EZbus LCD blank. so;ution: If for some reason the firmware updating process in interrupted (e.g., the USB cable is accidentally removed, or you have a power failure), the EZbus will not have the complete set of operating system instructions it needs to function properly. The most obvious symptom of this condition is the blank LCD. 1) If you are using the latest EZbus driver, you simply need to double-click on the firmware updater to reload the firmware into the EZbus. Note that you may have to do this several times, power-cycling the EZbus in-between each attempt, before the firmware will be successfully loaded. This is normal, and is not an indication of any additional problem. 2) If you are not using the latest EZbus driver, download the zipped file (below) for your operating system (Win XP or ME) to your computer's desktop, or a folder of your choosing WinXP Firmware zip: WinME Firmware zip: 3) Unzip the file, again to either your desktop or a folder of your choosing. 4) Navigate to your computer's Device Manager and highlight USB Device. Now go to Properties and click on Update Driver. Point the Update Wizard to the desktop or to the folder into which you downloaded and unzipped the files. At this point, Windows will reinstall the file EZbus.inf, which will allow you to refresh the firmware, as in Step 1, above. 5) Once the EZbus.inf file has been installed, the listing within Device Manager will now read EZbus-Needs Firmware Refresh, rather than USB Device. At this point, follow the procedures outline in Step 1, above, until the EZbus operating system is restored. " Would it be worth trying to download firmware code and trying a USB link up? going by the other person's experience, no point 2 and 3 button power-ups produced nothing. for the CPLD / TQ100 pinning CLK1 is 22.58125MHz CLK2 is 23.99700 MHz CLK3 is logic low clocks presumably related sum and diff fashion with the crystals 22.579200 and 24.57600 CLK3 , not from the USB chip, comes from VCO o/p of U3, a 74HCT4046 , whose sig in comes from U29 an 04 inverter whose input comes from pin33 of the CPLD functional blocks, which is firmly stuck logic H so vicious circle of inactivity. Incidently TP4 of 8 is the only one with any activity on , one of the approx 22MHz clocks. From the R&C of the 4046 CLK3 must be about 200KHz, I wonder what would happen feeding 200KHz or so into the PLL ? something to try on next powering up DC -20.8,0,20.6,48.8 white -12,0,12,48.8 10.8,-.6,0,-.25 6.6 5,5,5,3.8V U30 1.44,6.44 (i/p for 3.3V reg), 10.7 removed analogue board, rear board, same LCD message. Unpluged LCD and replugged, blank screen , just backlight If mains off for too short a time then Audio + System LEDs do not light Sometimes select M + Solo then MIX LED goes on GSR L.H.L sequence 860R to 3.3V and GSR goes to .3V
Diverse Devices,Southampton,England
Telephone number - the same number as it has been since 1988 but email is now the preferred method of contact so number deliberately not placed here.
I devote time each day to replying to emails.
(obscure/obsolete components,second hand test equipment, schematics etc) Postal: 66 Ivy Rd, St Denys, Southampton, Hampshire, England , SO17 2JN There is no point in contacting me about any of the above, the repair job may have been done 15 years ago . I cannot clarify or enlarge on any of the above.

e-mail  email address

A reserve email account is diverse9(commercial at) Please make emails plain text only , no more than 5KByte or 500 words. Anyone sending larger texts or attachments such as digital signatures, pictures etc will have them automatically deleted on the server. I will be totally unaware of this - sorry, again blame the spammers.
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