Renovating pot with push-pull switch. Due to hardened lubricant on the DPDT slide switch contacts If anyone happens to know a generic name or name of the manufacturer? push pull sw on pot Logo? is a Studebaker logo "lazy S" in a circle, M in a circle and then FE also use of J without a top bar as eJ. Used in Carvin and Trace amplifiers. If I was doing it again I'd feed a wire through the point marked "<" over the boss "B" that connects with the axial shaft of the pot , and twist over the body to keep the boss from moving and dislodging the spring. And no need to bend down the rear closure of the housing, 1mm graff paper. push pull sw on pot Didn't lose the spring but just in case dimensions are 0.55mm wire, 9mm arms , ends 9 mm apart, 2 turns minus angle between arms and 3.3mm o/d of ring. At mid position , maximum spring force , so not stable position marked between the > and < giving the flip-flop action. One section moves one way and the other moves the other way and vice versa. push pull sw on pot The flattish section with 2 nibs goes opposite the boss part of the other section. Hold together enough to add a small dot of hot-melt glue on each corner on the surface that slides in the housing, there is a bit of space there. Position the 2 parts as in the knob pulled out posistion , before gluing and check that it will go in the housing and over the pot shaft end. Now for the spring. Place the glued parts in an engineers cramp or similar to give some more temporary closing force, and easier to hold. Push spring, ring first, in through the side with the narrow slot leaving the arms outside enough to grab one , to force into the slot in the flattish PTFE-like part. Push both arms in , restrained by finger flesh in the larger hole of the other side. With a needle point or similar, through the narrow slot, force the other tail/arm into its slot. Remove the cramp carefully , in case the hotmelt is not suifficient, and so loose the spring. Replace in the housing and wire down as described earlier , just in case the glue spots fail before finitshing off the slide switch refixing. Break glue spots by pushing pot shaft. Which leaves the question - how do they assemble originally?. Something to do with the small diagonal slot in the casing and the large gap between the 2 white pieces that I did not really find a use for, and its non functional in use. My test for whether bypass switches, found at the external loop Send or Receive sockets betweenb preamp and power amp, need attention , even before dismantling the amp. Take one cocktail stick/toothpick . Hold at one end between thumb and index finger and poke the other end in the socket - if the contact breaks before the cocktail stick breaks ,about 150 gms over length of 65mm. Where twizzle stick fails to locate intermittant fault. Try heating with a hot air gun after preliminary heating with use of a dummy load. Try vibrating boards etc with a hand-held engraving tool with a nylon bolt fitted in place of the metal tip. Sharpen the bolt , partly, to a point with a pencil sharpener. Beefing up 1/4 inch jack sockets The notorious problem with band/stage amps, the guitar/mike leads making poor contact inside the sockets. For anyone saying replace, move to another thread. I don't see the point in replacing with much the same, that will also weaken at the bend, over a few years of use. The tip contact has to repeatedly lift over the tip and then drop down into the groove. The ring contact/s don't have to do this so rarely a problem there. Coupled with more "leveraged" movement at the tip with lead tugging. Requirements some 2mm silicone rubber cord from a fishing/angling supply shop Hama/Perler/Pearler beads about 2.5mm internal bore, (small coloured plastic rings) for making "mosaics" on a sort of pegboard from kids/craft shops. The outside diameter of the bead/s size chosen seems to move easily in the gap in the moulding of the socket for all the ones I've tried it on, mono and stereo. Bit of looped copper wire as a "needle threader" Artery forceps, again from an angling shop, or similar tool. Thin nose pliers Assuming chassis mounted , then cut a piece of cord 100mm long. For pcb mounted ones then about 120mm and suitable 4x 2.5mm holes drilled through the board. Being rubber you can safely deill through a track or two if constricted space (caution if for speaker sockets). No need to desolder any wires. Pics below are against 1mm square graph paper. 1/4" socket bodge Some people may think that the socket shown has a carbon insert as contact, not the case, a dimple that the lighting suggests is black. First one takes about 10 minutes to complete and about 5 minutes each, when familiar, for the chassis mount socket type. First shows the "needle threading" action. Second is the main assembly, thread 2 beads (all red in the pics) onto the doubled-up cord leaving a loop. Place a third bead in this loop and pull the tails to tighten in place. Place in orientation over the contact as in the pic. ,placed at the "hinge" end of the contact. Take one tail around the pin edge furthest from the mounting panel, under the socket and back up the other side of the other pin. Grab this tail with pliers, 10mm back from the free end, and slide through the bead in the loop, the cord will be under a bit of tension. Anchor the free end with forceps. Lace the other tail to form a cross under the socket Reuse the threader , pushed through the bead in the loop. Trap the free end of the second tail in the threader, a few mm back, and pull back through the bead. 2 such pieces of cord will anchor themselves quite well in a bead but to be sure, balance up the 2 free tail ends and anchor both together with the forceps, while finishing off. You can then pull the bead through the loop to its final locked in position. Position all the sections of cord and top beads so near enough equal tension throughout. Remove the forceps and melt a spot of hot melt glue between the 2 tail ends The insertion and pulling-out force for any 1/4 inch plugs is then noticably greater and much more reliable contact in use. Makesure the hot-melt or beads are not near any hot components when reassembled. And guitarists can throw away those cans of contact spray My guitarist clientele are much approving of the technoque although it seems somewhat crude, but then the action of these sockets is pretty crude. Beefing up a different type 1/4" axial type no info of any sort on the socket, no maker or generic term I'm aware of. This one from an Ashdown effects return with dodgy bypass switch. There are 2 places in the plastic body that drilling through coincides with holes in the metalwork almost as though designed to wrap some silicone rubber cordage (blue in pics) around the switches to increase the closure force, located in place by curves in the contact parts. Then cleaning the contacts. One hole in the metalwork is a bit too small for the shown cordage and needs pushing through, directed down through the inlet and pull through enough to then push back and around the contacts. Tip contact to the left and ring contact at bottom of first image. Beefing up open Switchcraft type. Twist some tinned wire around the 2 outermost solder tags , twist together and solder in , forming small radial projections. L>oop the cordage behind the switch contact and around the 2 outer terminals , so avoiding the plug touching the cod. Tie into a loop. Attending to a different type Logo Y with a bar and a right rotated C in a large C almost a circle . Patent nos 3536870 976235. Has a clear plastic panel on the face away from the pcb. Drill ionto the melted plastic rivets, then open out , clearing the rivet with a matrix board cutter. Lever up the inlet end while desoldering the pin at the far end that goes to the ring contact. Clean and pack with bits of silicone rubber where it will fit. Returning a band amp back into its case Without tearing up the heavy duty aluminium foil screening stuck to the sides. Just what you don't need rattling around in the amp , bits of aluminium foil. The solution I use is a sash-cramp used in the reverse sense across the back of the casing to open the gap a bit and a sheet of celluloid draped over each side , removed afterwards. Preceeded by cutting off jagged corners to the chassis, for personal safety reasons, if nothing else. To determine value of burned out resistors. Well approximate values anyway as excessive heat tends to corrupt the value before going o/c. For types that have split appart,desolder,connect meter to wire ends and press the broken ends together with thin aluminium foil in between.For spiral wrap types scrape the laquer in a line along the resistor to expose the conductive track,with prods measure the maximum resistance from either end to the point of break and add a guesstimate for the width of the missing section. Worked example: 1 watt metal oxide resistor discoloured rather than charred. Apparently reading brown brown black or 10 ohms. The "black" band at the centre of the body will be the most affected and perhaps the outer brown one was brown originally, as least temperature affected. Scraping axially to make contact there were 5 sections of about 200 ohm and one for the break so say about 1200 ohms The value , this time from schematic, should have been brown green red or 1.5K Cleaning desoldered SM pads before resoldering To leave a clean solder surface. After removing the original place a bit of plumber's PTFE tape stretched over the pads and remelt the solder , with the iron, through the PTFE TO220 , TOP3 etc mounting bushes/washers Not the usual nylon or whatever ones that I never trust for high temperatures (soften and deform over time, loosening thermal connection,runs hotter, melts more ...... Does anyone make them from whatever the plastic/mineral? is used for the body of power transistors themselves, what is that material , what is it called? . Maybe because of brittleness they would have to use smaller screws/bolts allowing larger washer thickness in the hole. I've got in the habit of cutting off the non-metal mounting parts of TOP66 type transistors, opening the holes of TO220 or TOP3 and using them as washers. Hacksaw through the body just down from the hole, cut into the copper, to release around the hole, to remove the "bush". Then open out the reciving hole using "drill saw" ( part drill part rotary rasp/burr) rotozip, torx wrench of Allen key form (also using the nurled part) file etc finished with a countersink bit to clean the edge. Use a stout glove to hold the transistor. That is if its not a practical solution to hold down with a spring clip. Too crowded is the usual problem. But if drill a hole for spring clip mount make sure you mask off the area around the drilling to avoid getting swarf into the electronics. Just because they call it high temperature, does not necessarily mean it does not compress/creep in normal but highly elevated temperatures, leading to premature failure of device. I'm after some insulated and mechanically strong enough alternative to plastic without having to drill into heatsinks for spring retention. If a source of PTFE rod suitable for the insert sleeve part when drilled, unless having to restrain abnormal lateral forces . I wonder if fibre reinforced phenolic board would be suitable for the washer, I'll try heating some. Of course that washer part does not have to be circular and cutting it square with a hole would be easier. The washer part could be a disc or 2 of that stiff plastic material found inside power supplies where there is a chance that some component will touch the casing, next to a steel washer under the bolt/screw head. For that matter I don't see a problem of using a mica disc or 2 then a steel washer for that part. Bodge repair for failed conductive epoxy joints. Push the section back with folded up strip of kitchen pan scourer, held in place against the casing or something. The coarse open random mesh of plastic fibres is insulating and quite compression springy. Damproofing the end of a single conductor cable To avoid condensation creeping, via capillary action, between copper conductor and the sleeving from an open end into otherwise sealed section. How to make or what sort of term or construction to look for in cable specs? Had a go chopping off a 2 inch length of hotmelt glue stick. Ground a crude chisel on one end of a length of 1mm rod and drilled/melted through the stick, pulled out while still warm. heated a copper wire cable core and pushed through. Covered with some heatshrink and a ceramic bead at the open end to keep roughly centralised. Heating the copper and sleeving with hot air gun and allowing the hotmelt to ooze out until contracted down, then cutting off bead section. Cut it open to check and seemed a good bond but will repeat and stand in some water with potassium permanganate on the upper end of the hotmelt section and leave for a few days. Repairing large desktop mixer amps To safely work on and move around. Brace with Dexion marked D or Handy Angle (slotted angle) marked H , H, supporting the angled top panel. Anchor the ends with cable ties to make a fairly rigid part cube structure.
May have to extend on or more leads a bit.
After taking this pic, decided to cover the
the angle with gaffer tape, piercing the holes ,
to give a bit of insulation , should anything slip
as the aluminium of the case can bend a bit when
opened up like this.
Send / Receive problems on band amps
While operating , push a toothpick inside each.
If very little force just from a matchstick size
is enough to break contact then they it needs attention.
Light duty impulse tester for clicking the sides of
SM resistors in a consistent manner if indications
are a component failure of one then check the
other s of same batch. measure R before and after testing each
I have a small adjustable automatic centre punch (spring loaded ratchet
release for easy centre popping of sheet metal). The minimum imulse setting
of that is 9Kg but found a couple of much weaker springs to try inside .
one gives range 1.5 to 2 Kg before the impulse, the other 2.5 to 3Kg range
of adjustment.
1.5Kg sounds worse than it is. Trying on the back of my hand is not painful
or self-mutillation.
Converting metal cased TO3 transistors for mounting as plastic cased TOP66
IRF.... for IRFP.... etc
Except for the most thermally demanding situations.
Find some brass or steel nuts,
2 hacksaw cuts to make a slot. Or some flat metal bar with
a couple of slots cut in.
Cut down some PTFE rod to discs , one around
each TO3 pin then one of the cut nuts around that.
Solder another one or more to those 2 using
a broken TO3 as template to take the heat ,
fill the holes with screwed up tin foil.
Transfer to the wanted one, solder some silicone
sleeved wire through the nut slots and one to
soldered to or solder tag bolted to the TO3 case.
wires usually go the short major axis of TO3 body for G,D,S pinning.
Use silipad
insulation rather than mica to deform slightly and
slightly locate the nut assembly or use mica/ grease
for probably better heat transfer.
Insulate a spring or bar retainer from the cap of the TO3.
If a pair with central bolt (with yoke) then perhaps cover the
bolt in silicone sleeving.
Push on star grip circlip fastener
Perhaps doesn't have to be round but with a star-form 4 way cut
so when pushed onto a rod, the star bites-in to act as a circlip.
Ground a seriously rusty carpenter's chisel, ground to just 3mm or so
wide and cut through the steel laid on a copper block
and hammering.
NiMH batteries, recovery from 0 volts.
If run down to zero, apparently unlike
the Ni-Cad situation of metal dendrite whiskers
forming and not very long term successful fusing
them away. NiMH ones do recover quite well
from zero.
Hint for using silver loaded paint
When repairing multiple printed silver tracks on membrane
keyboards etc lay down a large patch of silver paint.Then
when dried, with a straight edge,razor and jewellers screwdriver
scrape away the paint between the tracks,much easier
and neater than trying to paint thin lines.
Salvaging small SMT devices,eg 3 or 4 leg transistors
Score round each leg with a scalpel then cut under the pad
of each leg to remove.Then clean up each leg with a soldering
iron when demounted.
Searching for a buried wire or even trace tracing in a
multi-layer board.
Where you can only connect a signal to one end.
Make a sniffer from the pole pieces and coil of a
high ohmic relay.
I used a shallow flat pack (small diameter) 48V
relay as you used to find on
telecom boards, this one an NEC MR48S 24, 4200 ohms,
fixed to an empty ballpoint pen barrel.
Connect to an op-amp with high gain and feed into
a crystal earpiece. Connect an audio sig gen set to
about 1KHz, square wave and high amplitude
and sniff with the pole piece/s in
translating and rotation to zero in on maximum tone,
position and direction of the conductor.
For more discrimination connect a DVM on AC range
in place of earpiece and set sig gen at about 8KHz
for highest response.
For single connection, ie not current through the
conductor then detection distance with earpiece
only about 10mm but about 50mm for 8KHz and DVM.
Miniature thermal switch
For temporary use only , for thermal runaway situations
when checking power amps or switching transistors.
Fix one of these to the body of a transtor temporarily
wired into the supply.
A small button click switch , where you've previoiusly
depressed the button while covering with hotmelt glue.
The button will release if the hotmelt melts
Surce of ferrous shim of 0.03 mm or 1.2 thou/mil thick
Open up one of those anti-theft tags from shop
bought items.
Repairs relating to temperature effects or defects that appear
a few minutes after switching on the equipment.
Use a hair drier or hot air paint stripper on a very low setting
on areas of circuitry that could lead to the observed fault to
induce the fault earlier. Use freezer spray to try localising
by reducing the fault condition (cessation of oscillation
in temperature induced gain change parasitic oscillations).
Beware temperature effects do not necessarily warm the whole
component it can be a very localised effect at one junction say.
For tracking down squeals and other noises in electomechanical equipment.
Obtain a medic's stethoscope (or make up an approximation from 2 pieces
of polythene tube). Remove the diaphragm and fix a small length of
polythene tube instead. Wave the open end in and around the piece
of machinery to find loudest point.
PLCC chip removing tool
Anothe ruse for traditional sprung wooden clothes peg.
The spring, cut back one of the return parts to leave
a small stub . Hold in some large pliers and introduce
in/under, one corner at a time, of the chip, pulling
straight, not levering on the plastic surround which will
split. I don't
like trying to remove at both sides simultaneously.
Replacing audio cassette tape heads.
Although the engaging face dimensions of the head are the standard the position
of the mounting plate spot welded to the head is not standard when trying to
find a replacement. On the replacement head break away the mount and burr down
any lumps with a Dremmel and ball-mill. Do the same with the original and swap to the new head.
Bind the 2 parts together with thin copper wire and immerse the wire in epoxy glue.
Threading fine copper wire through sleeving
I needed to pull some doubled up , 0.22mm (9 mil, SWG 34, AWG 32) Cu wire
through small bore sleeving. Some 0.3mm nichrome heater element wire
stretched out until straight, worked rigidly enough, with "peristaltic"
movement as a mouse (does this term translate across the pond ?) . I was
probably lucky that "soldering" the copper to the ni-chrome made a
sufficient strength overlap join to pull 1 wire through but I doubt it would
work pulling 2 through, soldered or glued, because of added thickness of
overlap bulge, when I have to repeat the process for the double one.
Butchered mini-din socket pins are a bit too big diameter.
Angling supplies shop for trace crimps, 0.8mm internal bore seems the
smallest they go to. Grinding a lead-in chamfer on the leading edge , and
feeding through a tiny funnel of talcum powder did not work.
While at fishing shop , bought a spool of fine line. Just to try the
following but wasted my time.
Connect a source of vacuum at one end of the sleeving core and introduce
some fine nylon line at the other, set turning on a small motor .
In the end slightly flattened the end of the ni-chrome wire
on a small anvil. Curled it over into a loop that could take a
doubled up length of 6 lb nylon fishing line and
pulled that through. Moved the tug point and introduced
the doubled Cu wire and pulled back through.
Keep hands dusted in talcum powder, not soap or silone oil
, extended surface tension or whatever the problem hinders
with tight sleeving.
Caution about blowing out amps etc
Just as I was blowing out, with a 1KW Martindale, the crud of ages from an
amp and its 12V fans.
Thought - these fans act as DC generators if blown forcefully. Presumably
you could damage, if driving negative volts into ps or fan contol circuit.
Next time I will jam something in the blades before zapping one with 1KW of
draught.
As an experiment with no load other than DVM , neg to neg, 12V dc , 0.2A fan
, 1 foot from the nozzle of a 1KW fan then 17volt output from the fan I
tried.. Must have contained segmented magnets.
Turnuing the fan the other way in the airstream still produced "positive"
voltage.
I didn't try it any closer.
Intermittant combo/ amp vibration fault inducer
Anyone have any advice beyond just rattling connectors , contacts,
components etc with a bit of plastic pen barrel., plus hot air gun heating /
running amp into dummy load?
Turning a blunt point to a 5mm nylon bolt, in a pencil shsrpener, and fixing
the bolt head in the collett of a powered engraving tool, with a 5mm back
nut, makes an excellent vibration fault indudcer. You do need to use phones
via an attenuator to monitor the audio out, over the engraver noise.
Cutting a hole in 1.5mm/ 0.06 inch thick steel
The sort of gauge used in casings.
Say something like a 3 inch diameter hole, fairly neat, so something neater
than chain-drilling then filing.
No fancy tools available eg no slow rev hand drill, fly-cutter on a mill etc
No proper mechanical engineer was around.
Took about half an hour to cut a very clean hole.
Used a 72mm downlighting holesaw, working from one side only.
mm graph paper behind 42 teeth on the cutter so decided on keeping every 6th tooth and grinding back the rest. Black felt tip line indicates one of the untouched teeth. Hole is quite round and very clean, no wavyness, nicks etc and eccentricity varying only between 71.9 and 72.2mm in diameter. Left image is the approach side and right image is the breakout side. The grey smudgey line on the left image is my felt tip mark to show where to put the plasticene bund to retain a pond of cutting oil, not anything due to the cutter. I carried on cutting until broken through 3/4 around and then hand snapped the remainder. The breakthrough side had a thin and narrow swarf ribbon perpendicular to the sheet which cut away/fettled easily with a stout knife, the only finishing I did before taking the pics, other than washing off the cutting oil. As a standard hand drill in a drill press, not geared down, I had to stab at it, ie spin up / drop+cut / release/ spin up ... Had to pack out under the packing slab of wood under the steel as it was obvious the cut was uneven , missing part of the ring. For small (smaller than fan grills) for kit casing Added vent hole covers - use a kitchen sink strainer rivetted to the casing after cutting a hole with Qmax cutter or similar. Owner butchered mains fuse holder caps. Wrong sized scrwedriver blades hacking away the bakelite even down to live metal. I so often see it but rarely have an exact replacement due to all the variables, 20/1.25,1/4 turn / screw, deep/shallow, deep thread/ shallow thread etc. For recessed type, cut off the end of a "proud" type that you know has a recess inside the bakelite cap and has barrel not larger than the recessed one. Cut off the cap, clean up the cut surface and glue with epoxy to the original. Test tape for checking end of tape reversal / stop problems Find an old cassette type computer games tape of short run length and erase the programme Identifying surface mount devices from the alphanumeric codes printed onm the top Ranking of keyphrases to hit SMT codes in search engines, eg CO5 in conjunction with term "surface mount" so only a crude list "device code" 10000 "marking code" 8040 "SMD type" 5400 "top mark" 2400 "device identification" 1360 "standard marking" 375 "device identifier" 645 ( not very SMD specific) Also for Google searches, the NEAR AND function, narrows the target http://www.staggernation.com/cgi-bin/gaps.cgi oddly just trying it you have to place "marking code" in the first box and CO5 in the second, (in either order), 3 words, surface mount in the additional box may also reduce target pages. 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, SO17 2JN England