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, CDs and Radios, with some cross-over 
eg fault in radio section of a tuner-amp would be listed in radio section . 
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.

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

Audio Amplifiers

Akai AM A1 Amp
Poor volume and balance
Corrosion on one of the volume pot wipers,not worn track..

Alchemist APD22 Nemesis Amplifier.
Shorted ps electrolytic knocked out a bridge rectifier and over heated 
mains transformer to the point of catching fire. Only melted insulation allowed 
a mains short and rupturing of mains fuse. The mains transformer was 
probably 160VA,2x35V secondaries leading to +49V,-49V rails but only 50V rated 
electrolytics. Replaced all 4 with 63V rating and uprated both bridge rectifiers. 
All the active side of the amp checked out OK. 
The most important modification was fixing a 120 C degree thermal fuse in the 
neutral line thermally coupled but insulated with paxolin from the transformer ,held 
down with a piece of fuse-size/shaped recess in paxolin anchored to the chassis, so 
sandwiched between 2 pieces 
of paxolin covered in 2 pieces of heatshrink. Also had to replace the rotary 
mains switch. As an interim before spending out on the correct transformer and 
all 4 63V caps. It ran perfectly well to my way of thinking on 2x24V,120VA transformer 
leading to 
rails of +-34V. Also of note no bearing surface on the extender spindles on the pots 
and switches going thru' the casing. I also made up some caps to cover the exposed 
(gaudy of course) gold-plated 
speaker terminal posts inviting a short otherwise. To replace sliding 
top cover turn amp upside down to push home. Later found out the amp had probably 
been used on British 240V mains with selector switch in 110V position.

Arcam delta 290 and 290P ,1993
Blown by owner shorting the loudspeaker wiring , wiring 
both amps together and long term finecky 
poor function switch contacts.
Remove front panel via 4 screws.
remove 2 rear, 4 front and 3 pcb screws to 
remove main cover.
Only one set of phono inputs operate, switch selctable 
on the phono board MM or MC.
Motorised switch  for R/C use and also manual front panel knob.
I would not fancy desoldering that one by conventional means. No broken pins
or lifted tracks/pads. Desoldered the motor and straightened the bent over
pins while melting solder before hot-airing apart the whole switch
mechanism. Drilled out the copper rivet holding front sub-pannel to pcb, 
replaced with nut and bolt. Remove ASIC / PIC IC for safety
All conductors covered in black corrossion, but does all come apart quite
safely, after labelling. 
I tested the switches and also that bending the wipers had not produced
trouble with extra back torque and driving round via the motor.
Now its all soldered in, the safety clutch operates in one position, too
much back torque. I had tested before fixing the metal casing back into
place around the switch sections and there must be some sort of additional
strain/misalignment. Took apart to separate the clutch, packing out under the 
2 springs, with hindsight should have had less packing or just one 
attended to as now too much pressure.
Position 6, Tape 2, triangle ident is "TDC" down to pcb 
and diamond to motor side
Pair of contacts, inside, is between that triangle 
and diamond.
If pin 1 is on motor side of each switch wafer 
then pin 6 to pin 12(common) in position 6.
The 2 pin wafer has very fine contact pads. This wafer must 
be oriented relative to the other 3 so that the dedent action 
from the main shaft leaves a bt of leeway to 
the 0 side of position 1 and same leeway to 7 side of position 6.
Eventually found the first problem to be the second cog is worn
No broken teeth as such , just frayed/feathered tooth tips , in a very low
torque drive, reduction drive. And the feathering/bunching eventually causes
the gear train to stall.
It is attached, co-axial, to a fine pitch worm drive, with no salvaged
eqivalent around. Turned the worm plus cog assembly around on
the axle and glued a salvaged 1mm pitch cog to the other end.
One possible solution. Fix the whole switchbank rotated 90 degrees, with the
motor uppermost, and bridge ribbon connect the 23 active lines.
Leaving the original hidden underside of the wafers exposed so can add a bit
of relative rotation if required.
Its switching line level signals, so stray signal pickup from extra wire
should be no observable problem.
Check each stage of motor/cog replacement.
Try motor plus first 2 cogs driven from the amp board 
before connecting the main shaft etc . All wafers must be in 
a valid postion or the remote will not work.
Nedds a good 3V on a DVM The BA6109 is pulsed 
and current limited.
Mains primary 7 ohm DC
Main Rs 4x .22, 2x 5.6, 2K, 1.5, 2x1K
BA6109 x 2 motor drivers, 5534, 072, 2x 5532
IC202 heatsink leaning over and nearly touching power diodes 
, packed under and high-temp glued in place
Mosfets in or desoldered 190 ohm across Q113 / 13
10 ohm across Q112 / 12
Good mosfets DC measurements
3.3,43,0
and -40 , 0 , -43
and with mosfets removed but driver circuitry ok
2.1,43,0
-39,0,-43V
replaced shorted both IRFP240 with IRF241 
as plenty of space , with mounting 
arangement described in tips files.
load test for IRFP channel with thermometer propped over the 
relevant mounting part of the heatsink for each channel
For 4V ac, 400Hz , 21 minutes to stabilise at 24 deg C over ambient
For IRF pair and 2 spacers each and original grey "cloth" insulator to heatsink then 26 minutes to stab. 24 deg C over ambient
For IRF pair and 4 spacers each and mica then 20 minutes to stab. 24 deg C over ambient
If its not possible to find a suitable cog/cogs it 
may be possible to turn the worm gear around, fill in 
part of the end of the spiral , form a "pulley" in 
that and set a rubber band around it.
Cut into part of the junk metal that slides over 
carying the main shaft and mopunt a motor and 
pulley in a different position.

O is original worn cog, B is bracket, P motor pulley and 
A is the Ned Kelly aperture for the drive band. 
When first trying out it would not move reliably 
to the next dedent position. Because of through 
hole plating, or now , the lack of it on the common 
line there was a break so not sensing the 1 of 6 posistion.
I increased the size of the motor pulley, from the size 
in the pic as the r/c process was timing out going from 
1 to 6 or 6 to 1. All the front panel switch shafts 
are weak , with the front panel removed. and will easily break.
Final job - heat the Al dome of the control knob 
to release from the plastic core, hot melt heated 
and reset 1/4 turn around.
IR R/C coding
approx timings, repeat 110mS, 1 bit .83mS, 1 pulse 26uS
ident code 101AB011 then function code
AB=01 or 10 on alternate key presses.
propbably some errors in some of these data, reading off scope display
1/ code 8001, where 8 = 8 repeats of 01
2/ 700101
3/ 600101
4/ 70011
5/ 6001101
6/ 6001011
vol-/ 400110101001
vol+/ 400113
pause (CD)/ 0011010010113
Uses upd6124a and 432Kz? resonator, AB function not mentioned 
in the NEC datasheet, but no numeric keypad on this R/C .
So avoids say keypresses 123 being misinterpreted as 1123 if the signal is
blocked while pressing the 1.

Audiolab 8000A (Cambridge Systems) 1988
Low level but not distorted o/p on one channel.
The bush nuts on the vol and balance pots had become loose leading 
to rocking of the pots and breaking one of the balance pot tracks.
Replaced with 100 percent length resistive track pot instead of 50 per cent 
track pot (at full volume lower output because balance pot at mid range).
Still an intermittant problem of low level/crackling on one channel. 
Transpired it was the relay,at first sight seemed unlikely as it was a 4 pole c/o 
relay with 2 poles paralalled so unlikely a fault with both contacts on one channel. 
Looks like bad manufacture. The powered make contacts were only just making so 
with time/stressing first one (un-noticed) then a second one must have failed to 
consistently make good contact.
Notes complementary pairs of 2SC2922 and 2SA1216 //2SC2168 and 2SA958.
Main DC rails +42V,-42V.
On the left bolted to the left chassis plate ia a power transistor 
labelled 4 ,a 2SC3851 that runs very hot but seems to be normal

Audiolab 8000A ,1994
Catastrophic failure of one channel causing burnt hole 
in pcb around 470 ohm R746 and the adjascent 470 ohm.
Patched up and replaced all Rs ,Qs and but could not find the original 
cause of high frequency oscillation that knocks out the outpuut Qs.
To save replacement outputs replaced the 0.2 ohm Collector resistors 
with 2 ohm, 10 W temporarily, one of the originals had burnt out. 
If one of these droppers goes o/c then the 2, 470 ohm resistors 
overheat to charring so probably part of original failure mechanism.
Replaced 2SC4382 with TIP41C and 2SA1668 with TIP42C 
2SC2922 with TIP35C and 2SA1216 with TIP36C 
as 1/10 the cost of the Sankey types and B-E 
47 ohm resistors with 150 ohm. Also the plus/minus balancing 
resistor R733 changed from 1.5K to 2K to reset biasing.
Now the oscillation problem .
Runnning at 50 percent mains voltage with R733 increased to 2.5K 
there was low level 10mV at output,20KHz oscillation that with 
any signal injection by touching with prod would flare up to 
catastrophic level. Changing capacitance by touch in this R733 
area would change the frequency but no cause found for this 
oscillation. Changing R733 to 2K this oscillation stopped but 
on "click" overlevel signal input (eg the notorious fridge compressor 
switch mains borne clicks) there is fatal high level oscillation again. 
This amp is class B and DC coupled throughout which is probably 
part of the problem. As FET problems in scope amplifiers I have seen lead to 
spurious oscillations changed the 2SK389 for 2N5198 dual FET 
with pins orienrted D,G,S // S,G,D.
Added a 820pF cap between B-E on each power trannie.
Also two of the trannies that blew initially were 2 seated in the 
ali heatsinks requiring E-line format. I had ground down the 
D form cased replacements to get to fit so may be connected 
and next time would ball-mill open up the aluminium instead. 
There was also a problem with the Tone on/off switch and 
loose phono connectors at rear because the plastic surround 
is not strong enough to restrain the internal connectors with 
using robust signal leads. Dry joint on C709 polyester 
but not presumed the main problem.
Numbering - left channel say Q935 can correspont to R channel Q936 
or L ch Q718 corresponds to L ch Q818 - so R ch is hundred 
more or unit more than the L ch components.
Some voltages for the good channel at full mains power 
and no load starting with o/p pair and l to r or furthest to nearest
39,0.02,38.3 // -38.8,-0.02, -39.4
0.6,38.3,.002 // -.58, -38.9  , -0.02
38.3,1.2,.59 // 1.2,.58,0 // 0,-.58, -1.16 /// -.57,-1.16, -38.6
Then on 60 percent mains voltage for next bank of Qs
Q934 // 0,0,-17.7
Q936 // 17.6,-17.6, -18
Q938 // 0,17.2,17.8
Q932 // 17.5, 0, 0
Then 100 % mains voltage on good channel
Q809 34.8,34.3,1.2
Q810 -1.3,-34.9,-35.4
Q806 14.9,-10.7,-11.3
Q808 -35.3,-35.4,-36.1
Q803 -10.7,9.6,10.2
Q805 -10.7,-11.3,-11.8
Q806 10.2,9.6,-35.4
Q802 10.8,10.1,9.5
Q819 -1.1,-7.7,-8.3
Q801 9.5,<>0,-1.8,-2,<>0,9.6 (in staggered order)
Because of B class and DC coupling it is not 
possible to run this amp with missing output 
trannies without cutting the main power rail links.
Gave up with this amp - after 3 hours testing fine under load 
with no discernable mains bourne inductive dV/dt surge or anything 
- phutt and 2 blown TIP 35/36 again.

Cambridge A1 Amp.
Zilch not even power on LED. Both AC fuses blown. Output trannies OK but 
replacing fuses low level o/p level OK but turning up the level then both 
fuses blow after a second of bad distortion. The speaker line fuses remain OK.
The biasing in one channel via the preset had drifted too high presumably 
leading to runaway. Unfortunately I 
powered up with the pre-amp disconnected from the power amp and injected 
large signal into the unterminated power amp and blew both TIP2955 and 
TIP3055. Could not find a gain matched replacement pair but could ineligantly match 
2SC2577 and 2SB705.

Cambridge A300 v2.0 amp, later than 1998
No phono amp included, despite the 
labelling so added one in the area 
marked for a Cambridge one, for a customer.
Used the RIAA Phono Preamp magnetic cartridge design 
with a NE5532 http://www.paia.com/riaa.asp
 with excellent results,very low noise, very low hum
. Used 2 13V zeners and 
2.7K droppers from the internal +/- 30V 
at the preamp assigned spot 
and the ground taken from the power ground 
not the phono connectors. Breaking in at 
the links 1 and 2
This amp uses  22/33 ohm ?, 2 x 27 Rs, LM317,LM337 
3x JE340 , SAP10 py and SAP10 ny and +/- 41V rails

Cambridge Audiolab 8000C preamp 1994
Both channels function ok but with no or low  signal there is a low level
mains hum. Hum  for only about a third of full range of vol
control,when present it is constant volume regardless of vol setting. When hum is present the
setting of the tone controls makes no difference to the amplitude of hum.
The mains transformer was 30v-0-30v with 120 deg C thermal fuse. This unit 
is double insulated with phono connector returns commoned but not to ground. 
With the earth point disconnected there was significant voltage on the chassis.
138 V ac one of the secondaries to ground and about 110V ac chassis to ground. 
With 3.3M connected between chassis and ground there 
was 60V ac so 20 microamp of leakage between primary and secondary.
Although 500 V megger insulation test showed >200M between primary and secondary. 
On changing the transformer noticed one of the chassis screws was far too long 
in the area of the mains switch. With time the end of the screw had pushed into 
and deformed the insulation around the mains line at that position. It had not 
punctured through but is obviously undesirable so replaced with a screw only 1/3 the length 
of the original. So SAFETY NOTE NOTICE for all Audiolab amplifiers check the 
clearance of the chassis screw that protrudes into the area of the mains switch wiring 
and REPLACE with shorter screw. This errant screw was the cause of the hum, removing 
it and the hum went but the leakage ac remained so had to replace the mains transformer. 
Whether the leakage and screw problems were related i've no idea.
Replaced with 25-0-25V torroid and half wave rectified DC on main cap of 35V 
innstead of 42V but seemed to work OK. There is little power used in a pre-amp 
so I assume it is only there to give weight - the customer requires some mass 
for his money as well as functionality.

Denon DRM 800,1990
Worn rec vol pot. Looked like possible to remove the 
sub board without removing front fascia but no.
Non standard pot so rejigged a la tips files.
Record balance out so adjusted RT102 and RT202.
Confusing Rec function,not single button Rec or
 Rec + Play but Rec then Play.

Denon PMA737 AMP 
Spilt liquid damage with corrosion.
Replaced all obvious (corroded leads) components and 
replaced still functioning but pins corroded M5218.
Replaced M5218 with TL072 and biasing diode KB265 
with two serised 1N4148s.

Hitachi HTA-09 Tuner amp
No display
20V zener supplying reference for negative rail 
gone ohmic

JBL SA660 (James B Lansing ) USA amp from 1969
Awkward amp to work on as there is no chassis as 
such , when the covers are removed it falls into 2 
parts with wire-looms between.
In all the years of repairing all sorts of stuff with odd smells, I've never
smelt horse manure. (see repeat occassion _ Fender Pro Amp) 
Last time it was used (long ago) it went bang so treading carefully.
Nothing obviously gone bang and cold basic testing the electrolytics and
large Rs seem ok.
It was correctly altered for use in the UK but ominously the smell seems
strongest around the mains transformer, primary seems ok.
Removed the side dished covers to the transformer.
The smell is negligible inside it and nothing charred or smoke stained
inside that I can see, but the two 110 coils measure 4.4ohm and 3.5 ohm .
The failure occured a week after converting the 2 parallel for the USA to
both in series for UK which is another reason for suspecting the
transformer. 
On retesting the primaries , excluding fuse and switch paths they were 3.3R
and 3.7R which is not too removed from proper sorts of values.
But the mains fuse (correctly rated for uK) is still ok.
I'll have to carefully power up via a variac.
When it was "repaired" in the states the two 10 ohm resistors were replaced
in the Zobel shunt on each output as severely burnt.
This would suggest ultrasonic oscillation but there are no amendments to the
amp, just the 2 Rs replaced.
The reported pops were probably the two 2 terminal thermal? circuit breakers
in line with each speaker going open circuit, resetting themselves later.
Glass bulb devices , anyone any idea what sort or rating these are, not
specified in the schematics, just listed as JBL part number 13176.
I've now powered up to 150V , wired as 240V mains and all is settled with
75V on each primary and +-31V on the first power rails rather than +-51V ,
full mains . Proportionate voltages on each of the other 4 power rails per
each channel on this "T" amp. Cold testing of all major components showed
nothing untoward except the smell apparently strongest at the transformer
The smell may be from where it was stored and nothing wrong with the
transformer.
First , before winding the mains up more, is to determine where best to put
some hf oscillation suppression.
The two 10R replacements are fine this time but the charring on the
originals and smoke damage on the adjascent large wire wounds mean the
oscillation was on both channels. 
Replaced the 2 blue axial electrolytics on both pas.
Added 2 chokes to the + and - rails for the driver 
stages of each pa and 3 chokes in the line for 
the preamp, 3 because of the board layout, mixing up both channels.
Another possible problem is the tag board under the 
can caps, the support plate could easily bend and the 
tags touch the chassis whioch could also have 
created the bang. Paked out the stanoffs a bit 
and added insulted cover over the strip.
The front section of the preamp is isolated from the 
ground points on the pa and the pa i/p bay.
To test without setting up oscillation it is 
a matter of earthing across. Also for safety 
the "bonding " consists of the 4 chassis screws 
that tighten against insulated coating. 
So bond wire to the front panel back to the mains 
transformer and made a chasis bond point at that 
corner to take a mains earth wire , absent for USA use.
Had to remove the preamp inductors that were not 
suppressing oscillation , more like the opposite.

JVC A-K22 amp and T-K11 tuner
Dropped to floor pushing the function 
switch extenders into the sub front area.
No damage because the joggled construction 
meant they just unclipped when jarred.
Tuner bulbs driven by 11V dc.

JVC AX 2 Amp
Shorted o/p trannies on one channel and blown fuse.
Replaced 2SB755 with TIP2955 and 2SD845 with TIP3055 .Fixed with just one 
anchor screw plus insulating seat and angled to heatsink to solder to board.
The ground bond eyelet is required between main pcb and chassis.

JVC AX 11BK Amp
Crackly/intermittant non-function of 1 channel on 2 of the selector switches.
Remade all solder joints and packed out ,and glued in,the space between the rear of these 
switches and the heat sink to give more solid mounting.

Kam GMX800 audio mixer.
Failed LED power meter.
Small 56 ohm dropper supplying the LED circuit 
too small so heat affected solder joint,replaced with 1Watt resistor.

Kenwood KR 9600 monster tuner amp from 1978, 2 x 200 watt
Numerous problems due to corroded front panel 
switches. Intermittent loss of channel,crackles 
and loss of bass.
To access remove wooden case by removing allen 
bolts from front and through case screws underneath.
To slide of lay front face down on a couple 
of books and slide upwards.
Absolutely full of dust settling through top slots. 
Crackly volume control removed and all switches.
Remove bottom steel cover.
To recondition vol pot remove final cover ,pull 
off wiper disk. On levering 4 tags to release 
next section beware of dedent ball near the 3 
terminals. Ball mill in Dremmel to grind the 
swages back on the end of the Ali shaft to remove 
the dedent and wiper disk.
The switches have to be desoldered from the board 
(cases not soldered to board) then prize away 
tags to get to corroded sliders to recondition. 
Mark the absence of any links that are absent 
although silk screen printed as present.
Alps slide switches of that era had much stouter 
thickness of the cases so would probably crack 
the paxolin if forcibly prized off leaving the 
static lines of contacts soldered to the pcb.
Used mole grips (lock -jaw pliers) fixed to 
front anchor points on each switch 
and desoldered each in tern with hot air gun .
Mark 1 to 6 and 2 way or 3 way.
One of the function panel lamps was out,not actually o/c.
Bad construction bulb wires soldered to copper wire 
then touching pins (or maybe failed 
"spot welds") that are soldered to the pcb,whole covered 
in silicone rubber. Made proper solder joints 
after pulling off silicone . Covered stem of bulb (where 
it touches plastic surround) with PTFE tape. 50mA 7 to 8 Volt 
bulbs.

Leak Stereo 70 Amp ,1968
Smoke then loss of one channel and random crackle on other channel.
No channel - 2 of the 39252 had C-B shorts,burnt 220 ohm preset and one resistor.
Noisy channel one 39252 showing "fuzzy" junction between C and E,desoldered showed  
forward voltage of varying 1.1 to 1.3V.
Replaced all 4 39252 with CV10253 (because had more of these than 2N2102) and 
burnt / stressed Rs. Fixed a thin paxolin sheet 
over mains transformer for safety reasons.
To isolate problem areas it is possible to swap L and R preamp 
plug-ins and L and R power amp boards.
From Leak manuals ,equivalents FYI
(RCA) 39250 = 2N4036 = BC143 (80V selection)
(RCA) 39251 = 2N3055
(RCA) 39252 = 2N2102 = BC142 (80V selection)
RCA 16006 = 2N3055

NAD 3020 1982
Serious constant level of mains hum independent of volume setting 
but otherwise amplifying OK. Also pressing in the mute 
created horrendous noise in the output. I have looked at these amps before 
but never realised how exposed the otherwise useful (easy to connect / 
disconnect in situ) rear extension for 
the ins and outs are. Those connectors are soldered straight on the main PCB 
not to the chassis. Someone must have leant or even just carried the unit 
gripping/pressing the 5 pin "din" and cracked the board. This extreme 
edge connects ground between the chassis and preamp to the power side. 
The whole power side was isolated from the ground. Found a length of 
stout copper strip and high wattage soldered between 2 convenient 
solder points to bridge and reinforce the crack. Also wired the 
breaks associated with the tape in/pout.
No load - voltages on the power trannies
32,.04,.6 / -32,-.6,.04 / -32,-.04,-.6 / 32,.6,.04
Viewing front of amp moving forwards
F = marked face (not heatsink side) or the flat of D trannies facing you and B facing away
2N3055,MJ2955,MJ2955,2N3055 and 2xD669A mica insulated on heatsink
F D699A, F B649A , B B649A , B D669A
F D669A, F BC556A, B BC556A , B D669 A
B BC556A....................F BC556A
B BC 549C...................F BC549C
and to the left a D669A facing to the left
Large Rs 47,1W and 680,1W
Also 20mm fuse-holders needed replacing as breaking easily
 -age brittleness ?.

NAD 3030 1978 Amp
One channel went down in normal useage.
Although an insulated wire covering had melted in contact with one of the failing resistors 
this was probably a result rather than a cause. The Re 0.47ohm resistor with time had 
failed then taking out one of the 56 ohm Rs. Replaced all the 4 x .47 Rs with bigger 
wattage ones and the 56 ohm. All 4 2N3055 seemed ok,right biasing no overheating.

NAD 3130 amp
Blowing fuses 
Due to piece of swarf under the mica of one of the MJ2055 eventually 
puncturing the mica.

NAD 3225 Amp
Excessive audio mains hum and physical vibration 
of amp body
Delamination of mu-metal screening around
mains transformer-Dismount transformer,
prize away laminations and introduce varnish allow to cure
and repeat process on the other side.

Nytech CA 202 Amp
Get access removing one screw under front and three at rear
Blown channel due to broken banana plug receptacle at the rear leading to s/c. Probably due to 
back nut being too tight and ageing red plastic of the socket. No metal-work 
goes through the chassis to the outside world with these type of sockets so weak. Replaced 
both only finger tight backnuts but anchored as far as rotation is concerned by 
gluing a bit of cable tie between each bit of threaded red plastic at the back nut.
The power trannies marked N909 and N910 were exactly the same encapsulation 
as the BD909 on the ps board. So assumed N meant gain matched pair of 
BD909 and BD910 .Replaced the N909 with BD911 and N910 with BD912,slightly 
higher Vce,16 amp TO220. Replaced a s/c BC546B pre-driver with BC449
,BC640 with XTX753,BC560 to BC450,BC639 to BD235,replaced BC556C and BC550C 
and burnt 47 ,150 and 100 ohm resistors. Beware not all the original trannie legs 
agreed with the overlay graphics and some replacements needed swapping of leg positions.

Nytech CA 202 Amp ,1982
Crackle on o/p followed by low and distorted o/p L or R.
power-on LED took about 2 seconds to light 
and putting meter on pre-amp power rail 
,only 3.5V not 30V.
Probably a dry solder joint on the 30V ps board 
putting a tranny connected to the main 60V to 30V ,
TO220,BD537, pass trannie, in overload .
Replaced the o/c failed BC549 with up-rated BC449,
same pinning.
Added a heatsink to the pass trannie.
To pull ps board off mounts undo the nearest 
pa and demount the 3 thru-chassis 'connectors' at rear.
Undid the back nuts,slightly, on the banana sockets 
and spot glued to avoid usual Nytech problem.

Nytech 252
Blowing fuse as above but different reason
Both o/p trannies s/c
Replaced the BD909 with BD911 and BD910 with BD912.
If required to dissasemble after re-soldering BDs and bolting 
to heatsink. Unscrew h/s bolts then to reassemble glue 
the insulating washer/spacer and anti-shake washer and nuts 
in place ,then remove bolts and put in place again and reassemble.
Beware when testing these amps out of the chassis. 
If the half-rail voltage is up near the top-rail you've 
probably failed to connect the signal lead earth point to 
the power side earth rail.

Nytech CA 252 
Blown fuse 
All four power transistors needed replacing, both channels.
On one channel R119 , R121 burnt, on replacing and 
cautiously powering up, R119 overheating so replaced 
the other two pre-driver trannies on the HT side 
of the amp

Nytech CTA 252 and CXA 252 1980 ? tuner amp and amp
Crackles on output
Very little on the www about this except someone else
who seems to have been here before but no resolution 
of HF , LF conundrum.
I have the schematics for the CTA252 which is the tuner amp
version and the CXA seems to be a slightly more powerful
version (but no external heatsinks ,all active in totally enclosed
metal case) of the output modules used in the CTA 252.
So far so good . 56V instead of 48V on the power rails.
Now more that doesn't hang together
-incredibly thick guage (electic cooker wire ?) used for power rail 
wiring inside but 2 pairs of outputs, thin wire connected
to crappy 2 pin din (low power) speaker sockets.
The legend on the outside says for use with ARC 'B'
speakers ,ARC 101 ?.
A pre-amp ? low power output ? active cross-over?  daughter board
is also marked ARC 'B'.
This arrangement uses active cross-over at 
pre-amp level rather than at speaker drive level.
One output channel goes to parallel paired up
4mm banana sockets with one 2 pin Din
socket labelled 'L. F OUTPUT' and the other channel
to 'H. F OUTPUT' banana plus din , not left and right ouputs. Two
pairs of outputs but 2 each paralleled together -
what is this nonsense about ? . I don't think anyone
has ever been inside this amp and rewired or repaired
at any time since manufactured
This must be the craziest amp i've ever come across.
Fixed the relatively straightforward problems that
could not influence the functioning described and
could power up both parts. Poor solder and broken 
banana socket and another poor solder joint. 
Replaced all banana sockets with 2 nuts on each ,one 
inside and one outside the chassis and tightened 
back-nut fashion from outside (not relying on 
plastic surround to restrain nut force)
On its own the CTA with a preamp - amp bridge
on the o/p & i/p 5 pin din works fine but did replace 
cooked 100R headphone output Rs with 1W. 
Replaced broken meter lamps with 6V bi-pin 
lamps adapted by soldering QM connector pins 
to extend and broaden contactsto match wedge-lamp 
sockets.
On powering-up
On its own the CXA only seemed to work on left
channel, regardless of which signal line was 
connected via the 5 pinn din. But connect CXA to CTA via the cross-over
type 5 wire 5 pindin to 5 pin din then it does work
It would seem one channel is split into H & L 
outputs of the slave amp and the other channel is 
returned to the tuner-amp as H & L low level 
signals - one to L channel and other to R channel 
of the tuner-amp.
[ I gave up and returned amp to owner on the assumption 
I had cured the main fault, mulling over 
later I may have got the above para wrong. 
Perhaps one o/p of the CXA is L low and the other R high . 
Then the CTA o/ps L high and R low. ]
Unfortunately the owner has the speakers that go with
this setup in another part of the country. 
Balance and volume control is then ideosyncratic.
Anyone coming across a pair of ARC 'B' speakers
will have a mystery on their hands as well, as 
no cross-overs.
Weird or what ?????

Pioneer A-X320, 1986 ?
Blown o/p on one channel.
Replaced both channel's 2SA1263 and 2SC3180 with 
TIP2955 and TIP3055. The legs on the replacements 
needed lengthening , used cut down Varelco pins 
soldered to each leg. Insulated washers and stand-offs 
to clear the body of the transistors. The volume 
pot is very acccessible on this amp.

Pioneer AZ 370 Amp
No o/p either channel.
Low level signal present on both inputs to the STK4192 mark2 from 
a phono input. Amplified signal was getting to the first in the chain 
of 24V protection relays but no further. The base of the driver trannie to this 
relay was slightly negative after the 3 second settling period and stayed off.
This protection is driven from the main V+ and V- rails both balanced at 45V.
Presumably due to long term drift there was this slight negative voltage.
Put a preset in series with the negative rail dropper and adjusted to give a 
positive Vbe.
In passing the D.A.T.A linear databooks of 1990 /1991 give the pinout of 
the STK4192 mark2 as 18-263 the same as STK4131,4132,4141,4151,4152,4162,4171 .
Looking at Sony STR AV220 the p/o is the same as the STK 4182 mark2. The p/o 
table 18-263 has pin 9 labelled power ground 1 and pin 14 power ground 
2 which should be marked as V- supply pins to each amp.

Pioneer CA X700 sound processor
Broken slider pot slider knobs. For specious cosmetic 
reasons there is a plastic grill sheet over the bank 
of pots so that glimpses of internals is obscured or 
maybe (unlikely) reduces dust ingress. Anyway to do this the slider 
knobs have a joggle in them which makes them weak. Removed 
all such knobs and plastic grill sheet. From sections of 
250mm black cable ties fixed to the actual pot sliders 
with 100mm cable ties. Then hot-melt glue-string soldered 
into a firm bond. Reassembled and cut off excess protruding 
through front pannel and releived/chamfered the cut corners.

Pioneer SA 130 Amp
No output
The triac BCR3AM4 ,200V,3A was kaput so replaced with a higher 
rated triac.

Quad 405, 1985 Amp
Problem with an internal fuse holder and maybe 4 pin Din socket.
Interesting circuit detail is the low pass filter feeding to diac + triac 
across each output to crowbar and knock out rail fuses should there 
be a DC fault condition at output when exceeding about +/- 8 volts DC
 - so protecting the speaker coils.

Quad 405-2 , 1982
Intemittant loss of one channel, to low level and distorted.
Could not induce the fault and tended to the items as above, 
plus remaking solder joints on the wire-wounds and 
remade spade connectors and crimps.
Made up a 4 pin Din plug to socket 
with channel feeds swapped for the owner 
to put in line to see if the problem swapped channel 
but no further problem.
5 pin ,N1 and N2 network internals are on outlier of the schematics

"Repair" to a dead amplifier.
The owner bought it seen working but was not working by the time he got 
it home. Was not aware that the amp needed bridging line level signal 
links between the preamp outputs (L and R) and the main amp inputs 
(L and R) on the rear of the amp.

Rogers HG88 domestic stereo valve/tube amp
Dates on can caps were early 1964
One channel down. Checked o/p matching transformers and seemed OK 
on resistance. Between pins 3 & 6 of each o/p valve 90 ohm and 73 ohm 
for each channel.
Uses 2 EF86 , 2 ECC83 , 2 ECL86
Main signal line in pre-amp goes from i/p to selector sw.
To G of EF86
o/p A to function sw.
to 1 G of 1/2 ECC83
o/p at  A to tape output and tone control
wipers of "filter" pot to Gs of second ECC83
One anode that should be about 110V of an ECC 83 was not 
passing current, the voltage was at rail of 230V
On replacement, DC voltages at the A droppers either side of valves
EF86s 63,72,70,60V
ECC83s 107,112,193,194
To ECL86s 330 V on each large wirewound
9.5V and 10.2 V on the 2 1.5 K wirewounds
Replaced the broken speaker o/p terminal block with insulated 
wire through connects as only a narrow slot. Original block was also 
10 way cut down to 4 plus mounts.
Reconditioned phono sockets as in tips files , easy side plate access.
In case stock problem the earth wire was fractured at the cable entry 
gland so replaced mains cable.
The front panel looked like rust spotted corrosion. It is not ferrous, 
probably copper and the lacquer had discoloured to give an appearance 
of spot rust coming through "brass plated steel" and legends half gone from 
finger nails. Front legends
Selector - Disc Xtlal / Disc Mag/Radio/Tape Comp/Tape Flat
Function - Mono Dis / Mono A/ Stereo/Mono B
Bass
Filter
Treble
Balance
Remote Control,Mains Sw & indicator
on Rear i/p / o/p High Tape/ Replay Low / Radio / Disc X / Disc low
then 2 Disc Adj presets for both disc i/ps

Rotel RA 312 , 1974
No tape record monitor function
3 up/down pivoted arms opereate 3, 2 way slide switches for tape monitor
selection etc.
2 are now malfunctioning maybe due to being knocked.
Its easy to slide out the slide bar of each switch and each contact is set
as manufactured,to bridge A and B , B and C but a mid position would seem to
be used.
For this amp, when made, the detent bits have been removed from each switch
before being used and the pcb wiring to these swutches shows that the switch
action actually used is with contacts between A and B and B and C then B-C
for off which is of course a bit iffy even when new. The 2 limit-positions
seem to be set by plastic inserts that define the upper and lower limits of
the pivotting arm in each case. I've not come across this situation before. 
The contacts don't seem to be worn or
bent other than they should be. Removed the black plastic guides 
around the levers and offset a few mm and glued back in place.
Replaced front lamp with 12V bulb
DC rails are +/- 23V

Rotel RA 1312 , 1969
I assumed,initially, it was just lack of amp - preamp interlinks but no 
as switched option.
Nasty brittle, age hardened, single conductor, wiring loom and wire-wraps
everywhere - typical 1960s, probable manu date 1969.
Good stable +/-50V dc rails and cold "diode " checks of all the o/p trannies
look ok but the speaker line relay does not click over.
Thought i'd found problem I removed the large cap that seems to be for
timing thinking it was leaky and powered up and the relay clicked over at
power up, but replacing with a good one returned to always off.
The line back from the main amp settles out to 0V soon after power up so
that is probably ok.
Other monitoring is via 
2SC789 between rails  which was C-E short, leading to protection circuitry ,
replaced with a TIP41C.
6V festoon bulb replaced, operating original was 10R, probably about 0.5W
Many of the switches including LV ones on mains switches needed attention.
Voltages on wire wrap pins on main boards from front to back, including pcb side pins ,
no speakers or phones connected.
Top
ps + Relay protection board
37V ac,37V ac,49,-49,-30,0,0,0,22,23,4.4,4.4,0,30,0,0,0,0,0,0
amp
49,-49,0,0,0,0,0,0,0,0,0,-49
amp from underside
0,0,0.6,0.6,49,1.2,0.17,-49,-49,-49,-49,0,0,-49,-49,-49,-49,0.17,1.3,49,0.6,0.6,0,0

Rotel RX 403, 1977
Replaced broken volume pot with one without 70K/30K bass 
compensation, left disconnected, remove lanp holder 
panel for better access.
Festoon bulbs 6.3V, 0.25A
uses BA1146 , HA 1137
4x C1986, 4x 0.22R
C1884, A984

Sansui A505, 1983
One channel dead, any input, except for switch on loudspeaker pop.
Nominal 0V at L & R outputs.
The bias pin 13 was near + rail voltage but should be 
about -1.5V even cutting trace to this pin.
Cutting trace to similar pin 4 of the good channel (Bias ) was about 0V

Sansui AU117 Mk2 AMP
Blowing 1A mains fuse
One of the 3A p.s. rectifiers s/c and one of the
2SC1986 s/c.IC02 ,dual pnp replaced with two pnp
trannies commoned emitter thermally back to back,
R43 and R44 gone high ohm,C10 generating
crackle independent of volume setting and for good measure
one of the phono I/Ps not s/c of switch with no inserted
plug.

Sansui AU 666 amp, late 1960s or early 1970s
Reported fault, as i was only given disconnected board, 
crackle on one channel in high gain selection of phono or microphone.
Small plug-in board marked F-1281 and TP-N71
No unpowered problem found comparing L and R channels.
Replaced 4 , 2SC871 with 4 BC184L , 180 degree rotated.

TEAC AS M50 amp
Wavering volume 
The rear spindle anchor of the combined volume control and balance pot had 
been forced inwards by pressure on the front panel knob,so rebuilt and reinforced

Technics SH E60 Graphic filter 
Internittant total failure
Long term heat damage had brittlised the solder
joints to the 78N05,resoldered and added
a proper vaned heatsink to the original poor
excuse of a heatsink.

Technics SU V5 amp
Dead unit
The mains fuse next to the voltage selector switch was 
blown.Access this pcb by removing the single screw on the base of the amp 
and sliding the pcb off the pins of the mains transformer.Fuse knocked 
out because one of the two 8200uF,56V smoothing caps was s/c.

Technics SU X930
Intermittent power loss
Due to long term thermal break down of solder
on one of the TO-220 devices in the p.s.
Resolder and add a heatsink.

Technics SU-X955, post mortem
One that got away because the microcontroller is defunct.
But can anyone suggest the mechanism of failure.
This micro has a -31V supply to multiplex
segments of a fluourescent display of audio power level.
Seriesed to this negative rail is an 8V zener to bias the
2Vac drive to the filament of the display to -23V DC .
Some small dropper resistors in this linkage (100,100 and 33
ohm)
between -31V and the filament burnt out as though
the filament had shorted to ground. The ps section
derriving this -31V was unaffected. Three of the four
outputs of the micro to the 4 grids of the display
are10 to 20 ohm to 0V,so catastrophic failure
here at least. I asked the owner if there was a
nearby lightning strike but negative.
A previous repair in the ps supplying one of the 14V 
rails was pass transistor 2SD1265 replaced with insulated TIP41C.
Apparently a long term problem was running hot/ fan problem.
Also the output hybrid was not firmly held with the 
original screws. Replace each with a bolt and 2 nuts.

Technics SU Z35 amp 
One phono i/p channel down
Inputs to one side of the JRC4559 dual op-amp 
were at -ve rail voltage so replaced with a 
TL072.

Uher Z140, domestic amp (UHER WERKE MÜNCHEN, Germany )
Uher Z 140
Probably 1981 but looks more late 1970s with only 1 IC, HA12002 , dark
paxolin pcb etc.
Told it was non working before being put in a cupboard for years.
Power switch must operate via a small auxilliary transformer to power a
large relay over, to connect mains AC across to rectifier diodes and 350V /
470uF , then high V, low A ,DC to  inside a screened box , with 2 wires out
presumably low V, high A, DC.
Nothing obviously wrong except a 2SD330 on a heatsink was flopped over and
touching the small transformer grounded mount but D330 was insulated from
the heatsink.
No awkward smells or sights but I've not looked in the screened box.
Also has VG840 preamp, EG740 tuner and CR240 tuner with loads of spaghetti.
Needs the preamp connected , in proper operation, to 
switch amp on and off, switch up for on.
LED at mains inlet changes brightness for on (low)/standby (bright)
Blown HV electrolytic inside, not the big external one 
and o/c bleed resistor , could only read yellow band, but both 
halves of R about 200K so replaced with 470K, 2W, 
giving 0.84V wrt HV-. Only HV leads in are required to check 
the ps.
Main rails are +/-34V.
To check ps, preamp not needed.
Dual diodes 29807, CTU 2S and 299226 , CTU 2K
2x 2SC2789
2x 82, 2x 1.5, 350V, 10uF replaced with 2x 450V, 4.7uF
ps board does not slot into the slots 
of the housing but on top of it so the main transformer 
will fix to casing. Thermal sw needs a spring retained 
added as only one plastic fixing
Reassembled but the 2 side amp o/p panels removed
Earth link between ps and main connected.
About 320V dc to ps
cs14 29,0,0
CS16 29,0,7,7,
CS155 33,-7.4
-33.4,0,33.4 : 0,<>0,0,<>0 : -7.4,33,-33.4,nc,33.4
33V on blue to the sw.
2x PA conn, 33,4.7,-0.08, -0.08, -4.8, -33
CP2 , CP4 -5.26, -2.8, 5.5
CP8,CP9 disconnected for these obs
On another occassion, mains in LED changes brightness 
but no LED or anything on switching on the controller.
The main relay clicks over but no HV DC 
for the ps. Failed solder at the large relays. 
The lines 3 & 4 on CS 16 are the switch lines 
from the controller unit.

Velleman K4000 kit stereo valve amp from 1994.
Was working well apparently but the hum that was always there, but
acceptable level, has now increased.
Stage amps I'm more familiar with always seem to have the mains one at one
end and the output one at the other end. This has all three 
transformers only few mm apart. 
Not just hum but mains noise, eg dimmer spike noise.
It would seem to not have a proper grounding.
Specially thickened ground lines on the ps board, large ground interconnects
to the preamp and main amp 0V lines and input sockets insulated isolated
from chassis which is bonded to the 3 wire mains input at the IEC socket.
The kit construction literature makes no reference to connecting the
thickened ps ground lines to the mains bond point and seemingly relying on
earthing of whatever is used as a non-integrated preamp or external source.
What is the point of reinforced ps ground tracks if they conduct current
nowhere , only via signal line braid, so a safety issue as well
I only have the amp for attention which is line level input
to speaker output so no volume or tone controls. Added some insulated 
braid from the ps ground strip to the IEC /chassis earth point.
Cut back the excess of bolt through the mains 
torroidal that ended only few mm from the ps caps, and cut 
back some of the bare wire excess at the terminal strips 
otherwise seemed well soldered etc. The ECC82 preamp was low gain 
so replaced.

Yamaha AX 396 Amp
One channel down - dodgey relay.
Main rails 60V,-60V 2SA1695 ,2SC4468 pairs
Representative Vs on interconnects to main board 
A+B L/S and Tuner selected,no L/Ss connected
0,13,6,4.8
0,15.3,1,0,1.7,4.4,0,13.6,39.7,0,4.8,4.8
-4.4,5,40,0,4.9,4.9
-17,15.5,0,0,0,0,0

Yamaha CR200 Tuner amp
No o/p and blown 40V supply fuse
2 of the 2SC789 blown on one channel,replaced with TIP41A
but still no o/p,held down to 1.2V on both channels,due to shorted Q17 and
Q18 biasing transistors 2SA561 in each channel.

CD players

Bang & Olufsen Beogram CDX 2 , type 5161 , 1987
As a block of 4 non functioning probably a problem with the MAB8441 I2C
encoder, otherwise plays CDs in their entirety but cannot preselect tracks.
To release the display board, manually open the top flap.
Torx screws throughout.
The 5V supply to the display board is on the board next to the ps 
, on the other side is a cover that encloses a 200mA fuse.
But I was just wondering how these sensors worked (reliably ?), presumably
just relying on stray domestic rf induiced in humans. There are no metal
pads to touch on the surface but are under the plastic cover and each
"aerial" pad connected to the unbiased base of a transistor with a gain of
100 or so.
Incidently the keyboard + encoder of this one is much like the Beogram CD
4500 , CD 3500, and touch sensors as used in Beocenter 9000 , Beolink 7000, 
Beomaster 2400, Beogram CD 3300 etc.
The key action has to pass through 3mm of glass
Removing from the cover and touching the pins that connect through to the
bases activates that switch.
Any thickness/thinness of plastic covering those pins and touching then no
action.
There is a part loop of aluminium that is part of the overall casing that
goes around the edge of this key panel , connected to ground but I don't
see how that is involved
For the CDX 2 in front of me, 20 "keys"
Each transistor has the base connected to a pin that touches soft conductive
plastic in a well under the glass and each base has a 8p2 capactior to
ground and also a resistor in parallel but the value of that varies between
55K ,68K, 100K and 120K for no apparent reason.
Looking at the CD4500 schematics with 8 "keys" i would expect all the same
but there, that resistor, varies between 22K,27K,33K,47K and 56K,
transistors all the same SM BF840 and each circuit around 4071 inputs the same.
Just the to number keys as original;
120K,100k,120k,120k,120k,120k,120k,56K,56k,120K
Philips transistors PH77 on the CDX2.
The activation pin goes into this compressible conductive plastic (100 to
200 ohms or so) in plastic wells of the casing but on top of that is a 3mm
sheet of glass.
Even if it was very high lead content glass I cannot see how that would make
it conductive.
Today I will try a temporary drawing pin to one of these pins to see if it
needs an intercept area for rf reception. I would really like to know why
these spread of base resistors , almost as though selected on test, but are
written into the schematic.
There is not a left to right spread or, nearest the mains transformer is
lowest, or any seemingly rational explanation for the distribution of
values.
Also a bench supply through 10 or 100M to each pin to see what the trigger
level is of each "key" through the I2C encoder. Although all keys work by
direct touching as one block of 4 is not working through the glass I suspect
the state change level of one line of the I2C chip is different to the other
4.
Pushing a drawing pin in one of the base pins then piece of 0.2mm polythene
over that and touching would trigger but not doubled thickness, or 0.5mm
ptfe or through 1.5mm microscope slip glass.
Could not connect DC to any pin without the wires on their own triggering .
Connecting me to the pins via 100M ohm then no key triggered, 10M all
triggered and in range of 33M and 50M showed up the difference of ones with
base resistors of 56K compared to 120K
I changed the 4 problem key base resistors from 120K to 220K and
reassemble and see what happens or not
So much for all that palaver, reassembled but there were even less operative keys.
Which left just the conductive plastic that miust be causing problems.
I prized out one of these conductive plugs from its plastic well under
 the glass. There is a ledge in these wells, and now removed, the 
conductive cylinders are not solid all the way down but open to a hollow 
cylinder at the ledge which is very weak and splits at that point, before 
my getting to it.
The glass has some metalisation , perhaps nickel spray on the rear of the 
glass.
Screwing up some aluminium foil in these wells to make contact with the 
frail and resistive , order 1K across 5mm,  and then fixing compression 
springs to the base pins to touch the aluminium has solved the problem.
Also soldering a piece of 26mm square shim brass to the 10mm diameter drawing 
pin then stuck in a base pin, shows that the variable base pin resistors  
probably vary according to the (unseen as glass is glued to the plastic) 
variable areas of metalisation under each legend.
Trying 2 26mm squares of brass separated by 1.6mm 
of glass , measured 30pF.
With larger contact area (higher C ?) then finger injected rf would 
trigger easily through 1.5mm of glass or even 4mm of perspex.
As a refinement can anyone think of phospher bronze springs or something 
non corrodable for this application. I used ordinary steel springs. 
I tried fine heater element , whatever metal that is, but although it 
looks springy it is not reliably so - it relaxes. Or even where to find 
phosphor bronze wire from a non specialist supplier, to make some springs.
In the archives its obvious that a lot have peolpe have been defeated by 
these B&O touch sensors - but the solution is now in the public domain.
There was an internmittant ? error code coming up which 
was due to poor solder point on the wire that goes to 
the commoned inputs of the 4071. 
Also removing the tinplate cover to the MAB8441 may 
have been causing some intermittant problems.
Touch sensitivity must be back to how it was originally.
Just the vaguest of touches now trigger.
In fact putting the 1.5mm glass over the 3mm legended 
cover glass then they all trigger. Putting 4mm of perspex 
over the 3mm of glass some now fail to trigger but otheres still do.
Ineffective top flap lift - remove the clear plastic 
spindle support and while moving the flap squash the 
new band through the teeth

Cambridge D300 CD failing to play track 1, 1999
Firstly intermittently then eventually rarely 
playing any CD track 1.
Cambridge D300 with Sony main electronics 
including KSS 213C laser unit.
It read total number of tracks and time run but skips to track 2 
9 out of 10 times .
It is possible to play track 1 via front panel 
control reversing through length of track 1,starting from track 2.
Doesn't skip or stick when forced to play track 1 or 
any other tracks.
No notches or anything obviously wrong with the 
radial sledge mechanism or positioning of limit switch .
The final dual cog that drives the rack was very sloppy 
in its bearing. Removed the cog, twisted a length of plummers PTFE 
,pushed through the mount and knotted through the chasis. Tightened 
up the pivot but this was not the problem,but could not see the 
point of a double (anti-backlash)rack if the drive cog has a lot of play. 
Using a few  gummed shop pricing labels stuck 3 x 3 
to pack out 3 thicknesses on the top of the CD platter. 
This increased the spacing between laser and CD and 
the fault affected tracks 1 and 2. So reduced the Laser/CD 
spacing by removing the platter motor and packing out 
with a .5mm washer over each mounting screw. 
Adjusted the laser (power? ) pot to bring back into range.
No wonder there is a copper (shielding ?) cover to the main board. 
The quality of work hidden inside would be poor even for a bottom 
of the range portable CD ghetto blaster. Components all 
skew ,hand soldered,bent plain brass heatsink on the main 
motor drivers IC not making flat heatsink contact with the IC body, 
loose large ps electrolytic wobbling on the copper foil track of the pcb. 
AC supplies 12V main board,13 V front panel,14 V o/p board
Representative voltages 3 leads playing track 1 on connectors to CD unit 
ordered from front to rear, first 2 are platter motor difference reducing on outer tracks.
3.7,2.9,3.4,3.1,0,5
0,0,5,2.9,2.9
2.5,5,2.6,2.6,2.6,2.6,2.6,2.6,0,1.8,0,.16,3.5,3.3,3.3,3.1
last 2 (3.3DC) have about .5V p-p signal and last pin 
about .5V p-p plus 2V approx pulses per rev of the CD.

Camdridge Audio A1 and CD4 amp and CD
Intermittant noise reported as feedback in one channel
According to the owner the feedback would stop if he 
changed the amp input selector to another I/p and 
then back to CD but would start again maybe half 
hour later. Nothing wrong found in the amp,nothing wrong 
with the CD . The glitzy gold plated and Litz wire phono 
lead interconnect had a break. Nice looking Cambridge leads 
shame about the quality - what do you expect for 25 GB pounds.
The outer sheath grips in the connectors were inadequate , had 
opened out ,releasing the cable and allowing to break .
Clamped the 2 halves,bound with a few turns of tinned wire 
and soldered together on all 4 connectors. The owner was houseproud 
and regular moving of the units to clean underneath was enough to break the signal lead. 


Cambridge Audio D500
Failed scale illumination.
Unloaded supply is 13.4 V ac.
Mark all leads before removing 
leads to the front section.
Cut traces at the back of lamp board 
and added a diode, 120R and a bright blue LED 
in central position. Opening out the slot in the 
reflector a bit to acccommodate and removed green 
filter , leaving the white sheet.

Denon DCD 300
No functios on cd
The front pannel switches are not fixed to the pannel and 
one intermittently was janmming one click switch closed.

Goodmans Delta 806
Failure to read some tracks.
Lint trapped around lens and excessive amount of gooey grease 
on slide way.Cleaned all and fine.To remove the carousel remove 
metal channel on RH side then slacken screws on LH side and 
bend outwards enough to release the carrier.The bit of wood that 
drops out is a spacer screwed to the RH side of the top cover 
with the 2 small screws.

Hitachi AD7000 CD player
Intermittant CD carrier problems eventually complete 
failure to open .
Stretched drive belt.It is possible with a bit of jiggery-pokery 
to remove and replace the belt without removing the CD carrier.

Pioneer PD5010 CD
No display or control and noise like high voltage arcing.
The sledge was banged up against stop beyond outermost track and 
the lens servo was chattering to make the noise. Switching on the m/c 
after shifting the sledge to mid travel it would only move outwards not 
to the centre of a CD. The ribbon cable connector to 
the opto unit is unclipped and pulled away from the PCB. Unit labelled 
PH308 about 1985. Sledge motor drive band needed replacing. All around the 
CD carriage was broken plastic making it look as though someone had gone to 
town breaking bits. But I think it is the same problem found on old Philips 
car stereos where there is plastic moulded around steel and differential 
thermal contraction breaking the plastic. Severe backlash because the sledge 
lead screw was not anchored by the plastic piece near the motor. Packed out 
with a piece of rubber to reengage this plastic anchor that will move to 
gain access to the drive band. After all this the problem was a dry joint 
or poor contact in the area of the BA6109 and the connector to the sledge and 
platten motors. Resoldering all in this area and putting a set on the connector 
pins seemed to cure .


Panasonic SC CH11 / SA CH11 CD compact 
Stuck in standby mode.
Power trannie Q519 blown on main power board and R597 o/c on relay board.
Replaced the 2SB1185 with TIP32A and mica washer and R597 with 1ohm fusible resistor.
C and E voltages on Q505 were 28 and 14V and Q519 15V and 22V.
AC current through R597 in standby 35mA,Tape 170mA,Tuner 200mA,CD selected 280mA 
and CD play 450mA. This bottom power board can be accessed without removing the 
main amp board if the nylon standoffs to the transformer are cut and reglued later,
Unplug the transformer from the socket and undo the CD unit from the base.
The plastic housing to the SVI3101 will separate from the hybrid board when removing 
this power board. E in the LCD display is due to power disconnect not Error.
The original fault was with the CD unit an intermittent short in the platter motor.
This CD unit used the chipset AN8802,AN8389 and MN6627
To gain access remove the 3 pcb screws and desolder the 2 X 2 motor tas. Careful 
of the data ribbon to the optical unit,disconnect by pulling closure away from 
the housing and slightly lift away from pcb so it pivots to release the ribbon.
Grind off the swage nibs on the motor end housing. Before prizing off make 2 hooks 
to introduce through each of the 2 crescent slots to retract the brushes. Make from the 
wires of a 1N4148 and hold in place with blue-tack (the stuff for sticking to walls 
posters of tennis player scratching her gluteus maximus). Micro -swarf from worn 
armature was bridging one pair of slots in the armature causing short. Also remove 
internal such swarf attracted to the magnet using a magnetised needle. Reaaseemble and test 
as any out of alignment of back plate will bind the motor. Tested at 2Volt,no load 18mAmp.
Refit end plate in exactly same place as original to mate with the pcb.The nasty interboard 
wired ribbons need the plastic closures pressing towards the pcb to remove. The blue and 
white interboard connectors just prize apart in direction away from the pcb. To manually 
activate the tray and platter engagement the drive cog is at the front of the unit.

Philips AK601, 1990
The CD reader deck had been dislodged by someone 
meddling inside. Remove top clamp. Slide the front facia 
from the CD carrier drawer leftwards and unclip to remove.
Bend rightmost the supports to release the right side slot 
spigots for the carrier. Reseat main deck so it hovers 
on the support springs and the protrusions underneath 
the static chassis surrounds

Philips AZ1101/05 CD/Tape/Tuner 1997?
CD not spinning
Remove 5 long screws and 1 short on base marked with pointers 
to separate , remove 2 screws behind aerial to remove CD unit.
Taking the I/P H(ish) of the releavant 1/4 of the BA6398 quad motor driver
gets the motor spinning.
Taking the I/P L(ish) of the isolated inv buffer on the BA6398 also fires it
up.
The signal line to this buffer from pin 25 of the CXD2508 main micro is not
going negative of mid V neutral.
Focus/tracker coils hunt and sled motor moves on power up but no spinner.
Both limit switches function
Plenty of laser diode output on a test IR photosensor, when first started
exploring there was the usual deep red glow, now no visual red glow but
still plenty of IR on the photosensor when laser is on. 
Focus servo works 3 times but no output from focus processor to initiate
platter motor drive. Monitoring DC at any of the photodiodes, set mid
potential of 2.495V and varies at most 5mV as focus servo activates, but the
5V supply to the focus photo diodes is varying about 5mV. Monitoring
differentially between 2 focus diodes there is less than 200 microvolts DC
variation .
Dropping the power pot R down from 1600 ohm down to 500 ohm, the spinner
kicks in and plays without hiccup. I had a root around inside the optics
area and there was a cocoon of an insect inside an otherwise empty and non
functional section of the plastic housing of the optics, but I did't think
that was anything to do with the problem .
Silliest fault/syptom I've seen for a  long time.
When I originally took the optical section apart, down an inch long narrow
shaft
by veiwing angled and just about getting light down there, I saw a delicate
facetted mirror like a cut diamond which seemed like I supposed it should.
I re-opened it and thought I'd wind up some cottton into a long thin
string , douse in meths and clean this delicate facetted lens. Looked again
and the facets had disappeared , it was probably a minute piece of
iridescent insect wing that had been lodged there.
Returned power pot back to original setting and fine , also the 7808 is not
running hot supplying the laser.
A bug in the system.
The vol pot can be reconditioned quite easily by removing the 
2 screws that hold the plastic bracket with function change pivot.
The back of the pot can be prized off without unsoldering 
the pins


Philips CD 100 CD player
All functions but intermittant audio.
Replace the reeds in the double reed relay assembly.

Philips CD210, 1989
Broken drawer in/out  switch, drawer assembly much like 
Philips AK601. The front facia broken off the drawer 
front, due to a broken plastic clip. 
Drilled into carrier at each side and screwed blacked 
screws to keep in place. Unclip the black 
bezel piece to expose interior of LCD .Replaced the 2 blown LCD 
illuminator bulbs, O/C voltage 21.5V ac , with 2 parallel 12V 
, 9.5V under this load, lacquered blue.

Philips CD300 1983 CD player not bad for daily use for 20 years
CD carrier problem and intermittent crackle/static noise on both channels.
Carrier first seemed to be belt problem. Mark the position of the 3 cord passes
on the "dial cord" drum as there is a locus cam under this pulley that activates 
the CD top clamp . Disconnect the chassis fixing of this cord and put a knot in it 
at that end to take up some of the stretch as at end of adjustment range. 
Remove the motor sub-assembly 
and 2 circlips retaining the final 2 drive cogs to replace belt. Problem was 
actually initiating front panel switch problems due to poor soldering/design on the pcb. 
Remove the right hand chassis panel. Change of switch spec but using original 
pcb design the switch thru-board pins were too small for the holes and disc of 
solder rather than cones of solder and over time with creep or thermal /vibration 
had broken in rings over gaps. Also resoldered other large pins on this board. 
Especially as mains carried on this board increased the size of the screw holding 
to chassis (too fine thread for the thin sheet).
Crackle / static and high frequency whine seemed to be associated with the LM337T 
-ve regulator as again broken soldering in this area. But with 0V (contact break) on the output no static 
and -7V o/p return of crackle. Probably due to bad seating of SAA7030 in socket. 
Data on these old Mullard /Philips CD SAA7000 series ICs (probably manufactured 
in Southampton) in Signetics 1984 Linear LSI manual.

Philips CD300
All control functions and output but flickering track indicator LED display.
I could not activate this fault and had to rely on the fault as reported by 
the owner. There are 3 ribbon cables to the sliding carriage. Disconnecting 
the ribbon nearest the CD platten the Unit would function fine but no LED 
display. As this ribbon touched the corner of the frame of the mains 
transformer whenever the carriage retracted to play position I assumed 
problem was in the ribbon but could not find it. Disconnected and 
refixed swapping ends and tied back all 3 ribbons so no longer could 
touch the transformer. Unit did not come bouncing back from the owner.

Philips CD610
Some CDs jumping.
Touching the CD while in motion to slow it down sometimes would not recover in speed.
The top clamp was not holding down to the top of the CD sufficiently on some CDs.
Unclip the clamp peripheral holder from the "hinged" plastic mount. Beware of 
a ball bearing inside that transfers the hold down force. Force out the top washer from this holder and 
abraid radially the plastic surface that touches the CD .
For general info . The wires to the front panel from L to R 3 wire 6Vdc 1.7Vac,6Vdc 1.7Vac,27V and 6 wire 
0,4.6,0,4.6,5,5 in standby mode. In play the secondaries of the mains transformer are 3.5V and 33V ac

Philips ND7500 
Very feint audio L and R on CD mode
The function select switch needed replacing (6pole 3 way).As usual 
awkward to get to.To avoid damage undo 3 connectors to the CD unit 
and undo 4 retaining screws and remove unit ,undo and mark positions of 
the lightly held leaf spring limit switches on the cassette decks ,mark the 
tortuous path of the tuner drive cord should you dislodge this and unsolder 
a few of the earth wires and aerial connection to allow enough 
freedom to open the whole system up to work on (not many interboard connectors)

Roksan ROK-DP1, 1991
More mutton dressed as lamb , CD platter not spinning.
Uses Sanyo , LC6554H4301, Sanyo LA9200N, Yamaha YM 71221B 
motor driver probably (glued on heatsink ) PA5205P with Double E logo, 
so main electronics probably stripped from a very basic ghetto blaster 
and built into a huge heavy box with basic ps and a cct for 
driving a Futaba R/C model boat servo to lift the CD flap. 
This servo glued to a bent plate that is fixed to the woodwork 
with 2 wood screws. Wood painted matt black and front panel 
painted to look like anodising, original display bodged 
into place. The main board nylon standoffs are for different 
thickness baseplate so can easily dislodge with track side of the 
board touch the base plater.
No DC on the BA10358 ? 8 pin SM marked 10358 
XRGA dual op-amp ? although laser-on , initial 
few seconds power-up signal was 
getting to the pass tranny, only 100mA 2SA608.
Tiny 100uF,6.3V electrolytic logo S in a square diamond 
had failed on the laser unit, loading the 5V power rail. 
The sledge drive belt needed replacing.

Saisho CD595
CD unit would only read the TOC track and nothing else.
This uses the Sanyo SF91 pick up (moulded on junk-metal 
casing).The final 14 tooth cog that drives the sled rack had 
2 teeth worn to nothing.Presumably after long term chattering at 
one end or other of the sled rack but no reason for this found.
The final double cog from scrapped SF90 is not the same so rebuilt 
the worn cog.With ball mill cut back remnants of the 2 teeth and Drilled 2 1mm 
holes through the mian flange. Glued in two pieces of wire,plenty of space 
on other side of flange to anchor the wires with glue. It would have been better 
anchoring the wires at the other end as well but this would have fouled the next 
cog in the train.

Saisho CD616 portable stereo.
Broken and missing catch for the CD cover ,the leaf switch OK.
I knew there was a reason I made a collection of odd metal and 
plastic linkages,arms,pivots etc from scrapped VCRs and audio 
decks.Fashioned a replacement from a plastic pivotted linkage and a rod for the 
pivot from the main base plate of a scrap VCR.A small light action 
compression spring behind the pawl of this new catch anchored to the 
case with hot-melt and a longish heavy duty compression spring to 
link curvily between the release button and the part of the catch arm on  
the other side of the pivot.

Sony CD 104 old CD
Distortion on both channels like clipping of over 
amplified signal.
Replaced the SAA 7030 filter IC

Sony CDP 35 CD unit
Rejecting, intermittently, CD and some skipping on first tracks.
Rejection due to permanently bent limit leaf switch that monitors 
CD carrier in and out extreme positions.Reinforced the outside 
edges of both contact leafs.Skipping-changed setting of  
the laser power pot ,as this was only 10 per cent of the 
whole 5Kohm pot paralleled a 1K SM resistor across the pot 
and reduced value from 450 ohm to 400 ohm.

Sony CDP 671, CD, 1995
Suddenly stopped playing any CD just registering "No Disc"
Removed the top housing from around the top of the deck, 
separated the two parts of the top spinner to remove, 
reassembled and placed over a CD and it worked for a 
couple of hours and then totally dead.
To remove the optical unit unclip the 2 clips 
either side of the top frame to remove and then the 
carrier can be removed , reverse for re-assembly.
To operate without CD carrier and top rotate the 
helical cam that lifts the deck into play position until 
touching the leaf sw. 
I had deliberately played  the last track and switched 
off at mains just to check whether it was possible to 
clean the lens without disassembling.
In the process of extending the final ribbon connector 
one conductor had failed again. Laser unit KSS 213B 
dated Dec 1995.
Break line connected the laser to pin 3 of the CXA1821M.
Desolder the platter motor, remove pcb screw and 
2 screws on the sledge motor. Release the 4 suspension 
screws enough to give space to extract the sledge 
motor helical pinion through the base plate.
Poor man's Litz wire , 6 wire twisted 46SWG to bridge between PCB solder points for that connector and one either side on the assumption 
that they would fail next. Choose enamelled wire 
that the insulation will melt with soldering iron. 
Double up 6 long lengths , mount one end in a 
dremmel to twist up, solder at 4 spaced points along 
the wire and cut into 3 lengths.
Other main ICs CXD2545Q and  BA6392FP.
DC voltages on main ribbon to optical unit
from front to back in play mode
5,4.7,4.7,5,5,5,5,2.5,0,4.7,.02,5,.09,4.4,4.8,2.5,2.5,2.5,2.5,2.5,7.1,0
mechanical lead .5,.5,0,0,0

Sony CDP C100
Failure to read TOC on some CDs and fine playing others.Measured the 
apparent ohms of the setting of the laser power pot.
Adjusted laser power pot 5 percent one way of marked initial 
position and failed to read any CD.Turned 5 percent other way 
and all CDs could be played,optimised this position and left  
it at that. As a side note trying an extra large 
CD (diameter about 2mm greater than normal) caused the returning 
CD to jam against the carousel.

Sony CDP M20 cd unit
Would not accept CDs
CD carrier would enter the unit but the rotor unit would fail 
to engage with the CD because of stretched drive belt.

Sony KSS 180A CD unit
Sticking sledge.
By marking each cog and playing, problem 
recured in same position of first large cog 
after the motor drive cog. Break away the 
plastic retainer to remove the cog. 
This seats on plastic and grease. Cleaned out 
the grease and added a graphited running 
washer salvage from some other bit of kit.
The cog that drives the rack had a lot 
of play so that the anti-backlash secondary part 
of the rack may have jammed also. Partially 
broke and re-glued this retainer so lot less play.
Reglued the other retainer.

Sony RX88 , 1998
Intermittent non-play or skips
On arrival no play at all.
Too much crud falling through the vents on the top , 
thorough blow out , cleaning of lens etc and added 
a couple of angled deflector plates under the vents 
to direct the crud down the sides , away from the CD area.
Remove the 2 screws plus spring under to remove the 
top clamp over the CD unit.

Technics SL PG 490 , 1994
Post Mortem
From cold would play a CD but not any others, would 
not read track data , returning "no disc"
Error Code FTC on display when pressing 
play+stop+pause on power up after warmed up 
and playing up. Also while at it disconnecting the 
main data cable gives error code F-26
Holding an IR phototransistor connected to DVM (ohms) when cold then 
laser output would give 440 ohms minimum gradually increasing 
to tens of K.
By comparison 6 inches from 100W pearl mains lamp 
gave reading of 410 ohm. Checked the feed-forward laser power 
control was working if enough signal from the coupled photo-detector 
had been sufficient. Removing the optical unit and 
powering from a ps with droppper Rs gave 2.59V over the 
laser when cold dropping to 2.46V and very low level 
visible glow from laser.

Technics SL PG200A CD, 1990
No CD playing. 
One of the 2 springs that hold down the top platter clamp 
was missing but only incidental , real problem was with 
platter motor
Also Low level flutter noise on the headphone output. 
Not dependent on motor speed or play or pause mode but 
due to earthing problem / smoothing on the 8V line.
Not attended to as only noticeable with headphone level at minimum.
To remove the CD transport section the third screw is 
under the deck and requires removal of front pannel then slideway 
to get to screw head. Main 2 ribbon pinning designations on 
the underside of the deck board.
Platter motor showing 2 ohm in say East or West stopping 
and 12 ohm in N or S. So if stopped in 2 ohm position would 
not start. Pulled off platter ( "hub puller" in tips files) and 
replaced motor, gap under spinner was 60 thou. Uses TDA8808T and TDA8809T

Venturer DM2001 personal CD player.
Dead machine except charging light on charging.
The door closed leaf switch was mangled but as was very flimsey 
anyway replaced with a beefier one salvaged from something more robust 
and hot-melt glued on.On opening beware of the laser unit not positively 
held to the 3 springs and the function switch levers are not held firmly either.

Yamaha dual audio CD recorder and player
Someone asked me to look at this very expensive unit , but I declined.
Not seen and model number unknown.
Apparently there is something called OPC that checks the material of the
blank media. About 2 out of 10 attempts to record, it drops out at this OPC
check stage, equally so for the 2 makes of disc he uses.
As it is still useable I declined to look at something that may well end up
worse, and I suggested he try some other makers discs.
I did a bit of reading up about the technology in and around
http://www.chipchapin.com/CDMedia/cdr3.php3

Radios

Blaupunkt BP0491 (1994) (Renault car) Car stereo
No sound on either channel in tape mode.
Someone had tried fixing a problem on the tape unit probably flimsey microswitch 
tape-in problem. They did not know you have to desolder from the base of the PCB 
the phenolic ribbon cable to the tape heads before demounting the tape unit.
They had broken this ribbon. Repaired in manner described in tips files with 
a much longer piece of standard ribbon soldered to the remainder going to 
the heads as narrow access to solder to otherwise. Anchor this standard ribbon 
cable to the cassette sub-unit chassis near to the audio head.
For powering up on the bench. The rear connectors consist of 6 rows.
Bottom row 1 leftmost (1) 12V to front pannel bulbs,2 via 220 ohm for 
memory 12V,3 power to LCD display board,4 earth.
Row 2 no 4 12V supply to fuse, no 3 switched 12V out
Row 3 speaker returns
Row 4 Speaker lines
Row 5 and 6 external signals 

Blaupunct SQR 88 car tape / radio.
No display
The owner had made a mess of rewiring and had probably 
taken the powered antenna output to ground which burnt out 
 part of the track on the main PCB near the o/p which also supplies 
part of radio and display.Also when repaired 
the unit was taking about 1amp when switched off on the front and 
one channel was down ,the relevant TDA7241 was 
shorted between pins 6 and 7.

Decca Deccalian 90,1951
with Garrard RC70 and Plessey record Deck.
Tuning dial string needed retensioning. 
Remove knobs and then release the bolts holding the 
amp, don't let it slide. Undo the 4 large bolts enough to 
release the drawer runners to remove the record deck. 
Weights are cabinet 12Kg, Deck 9Kg, Amp 6Kg

I was surprised magnetic cartridges were around in 1951.
Also surprised at the strength of the magnets, the steel
rule in some of the pics had to be some way from the bakelite housing or
they grabbed the rule. 
Unit was 67GBP 4s,  in 1951 which translates to 1,364 GBP in year 2000, via
"shopping basket" RPI calculator
With Decca type D magnetic pickup on a Decca Deccalian 90 radio-gram .
The mechanism was dislodged or jammed so the tone arm can move vertically but
not rotationally to engage a record. Firstly remove the cartridge, 
bayonet fitting, the coil DC resistance was 3.4K. Tie the deck to the drawer as it is not 
positively fixed. Remove the central bent record rod and in case the 
platter should fall off in viewing underneath, remove or push a grommet or 
something over the central spindle tube.
I thought initially that something had gone seriously wrong to bend the
spindle as it does not look like an engineering job , but finding www pic
http://hem.passagen.se/sodas/articles/rc70.jpg
that is normal.
Something had seriously jarred or a tinkerer been at it so that the end stop
for the rotational  movement arm under the tonearm seemed to be on the wrong
side of the linkages from the main mechanism.
Slackening off some of the pivot points and the base of the tonearm pivot
I've repositioned and that is now moving freely.
There is still something wrong as the motor-off mechanism is falsely
engaging after motor start unless I hold back the linkage that breaks the
switch mechanism and then it can latch into normal motor run, disconnected
from all linkages, until delatched via switch off or by tonearm moving to
lift point.
One turn of the main cog wheel is the operation cycle time to complete
record drop , arm lift/drop etc before coming back to the toothless section
of the cog for all mechanical levers disengaged and motor-on for play.
Just before the toothless section the large cam pushes a set of levers to
switch off the motor and no obvious extra latch or anything to disengage
that action for each turn of the large cam, so it turns off the motor before
going into disengaged play mode every time, presumably the same action as
manual reject on the on/off lever.
It would have helped if I'd seen one of these decks in operation but I think
I've cracked it.
Reject does not mean reject from play followed by motor stop , it just means
reject from play. You cancel the motor by manually switching to off or what
I assume is the proper trip mechanism . If the tone-arm goes in too far and
the normal lift mechanism fails to operate then the trip is de-latched to
switch off the motor - ie not normal operation. The cam position just prior
to the cog teeth gap is for setting this position , just less than trip ,
not for tripping the motor off. Original problem before someone got inside 
was probably the tonearm radial assembly fowling on the lever that 
sets the trip position. Repositioned yet again so the lever with 
roller engaged the proper part of the tone arm underside to 
retract the tonearm back to rest position at end of cycle.
The anti-skating mechanism. I don't want it to be too
resistant to movement and break the original stylus. Cartridge and stylus
removed during all this exploration. I'm thinking of removing the stylus and
pivot from the magnetic coil and lightly gluing some bulk-standard LP
sapphire stylus underneath on first checks with records.
The anti-skate mechanism is a small vane like an air brake of a chime
mechanism escapement of clockwork clocks or clockwork automata.
One edge of this vane on a deliberately floppy pivot/axis anchored via a
very light tension spring and the other edge rubs along a fine toothed
ratchet in the easy sense until the end of travel at lift up point on the
record and then released from the ratchet. Manually , ie excessive outwards
force on the arm also trips this mechanism after "jamming" in the ratchet ,
but not by normal anti-skate forces.
By finger touch feel on this arm , the reaction against the ratchet clicks,
which would have to be provided by the stylus seem rather too strong, the
clicks can be felt. I put a force gauge against the end of the arm (minus
cartridge) and this against the ratchet force is about 6 to 8 grams and
about 15 grams final lift up trigger lateral force, perhaps that is not excessive
but the sapphire stylus is quite long, about 2mm, so much longer than any
60s/70s LP stylus sapphire. Perhaps I should be more concerned about the
final lift trigger force.
There seems to be no anti-skate adjustment built-in and is all under the
deck so would be suck it and see adjustment.
Made a stand-in replacement stylus from hacked off part of standard 60s/70s 
stylus  
with a tiny part of the aluminimum stylus
shaft and superglued (later added epoxy) to the pit at the end of the steel shaft about 1.5
mm internal diameter , outside diameter 1.8mm and about 2 mm deep above the
solid part of the steel. Steel was high carbon steel for clock repairs so 
had to be ground cut. Brass pin and 2
pieces of moulded hot melt glue painted black form the soft anchors.
The manual says it is sapphire but does not state what weight at the stylus.
As it is, its about 25 grams , seems about right for that era, could not find 
specific info.


Ferguson 3195, 1960s radio
Distorted audio.
Replaced output CS9013 tranny with reoriented BC337 .

GEC G836 SW receiver (1968 vintage)
No audio other than amp hiss on all bands.
The AF115 mixer/oscillator was ohmic between case and emitter.
Replaced satisfactoraly with AFZ12.One of the 2 AF116s 
had an intermittant internal fault and replaced this 
with a AFZ12.Totally worn out Vol and tone pots

Grundig 2035W/3D/GB, 1956
Poor AM reception and even poorer FM reception
ECC85,ECH81,EF89,EABC80,EL84,EM81
Before removing the chassis from casing mark and 
desolder the speaker connections and the magic eye 
spring retainer, and earth ? point on underside 
cover plate. Extend the main speaker leads only 
to check out of cabinet. On removing the glass dial plate 
beware of dislodging/losing the protective rubber 
channels.
Broken stringing, 5 separate string runs, use 
cable ties to hold the ferrite rod onto the 
rotating yoke.
AM stringing run - pointer at left of scale. From the tuning 
cap pulley comes of the front of 3 turns to the 
right to the underside of the front of the front clutch 
pulley, 2 turns, off under to the R to small 
pulley on extereme r, 1/4 turn angled up to 
large pulley,1/4 T to top dial string with 
tension spring near lamp bracket, to pointer top 
clamp,  to L large pulley, 1/2 T returns to tuner 
pulley innermost groove.
3 static strings -  for locating each pointer.
FM string run, pointer at L of scale.
2 turns on tuner pulley, innermost angled down 
to large pulley, to bottom front of rear 
clutch pulley, 2T , off at bottom , under the 
AM vane tuner, in line spring under this 
tuner, to extreme L large pulley, 45 degree down 
and in to L front pulley, to pointer clamp, to 
R most pulley, 45 d up to under side of FM tuner pulley
L hand tone control - , string off front L to 
brass cylinder , 45 D up to red indicator
R most tone - , from front anchor clockwise then to indicator
Ferrite rotator - rearmost off the knob pulley 
through up spring, to rear of ferrite ali 
rotor off front to frontmost of the 2 paired 
pulleys , back to knob pulley. Tensioner in long 
frontmost section 9 3/4 inches from spring to 
knob pulley anchor point
From my radxref.htm file and inspection this circuit is 
much like Defiant MSH 755 without push-pull paired 
EL34 output and divider/driver. EL34 grid resistor overheated 
so could not read value, measure in circuit as 1.28 K 
and then 21 ohm back to HT1
Rattling noise on turning tuning knob due to trailing side 
of clutch rubbing on bumpy surface, loosen flywheel 
screw and move further from the trailing suface.
Replaced ECC85 , replaced mains lead and took live to switch line, 
2 lots of stringing, 
tied down the ferrite rode to yoke with waxed thread.

Hacker Sovereign II ( 2 ) 1970 radio
No o/p. Probably corrosion on the 3.5mm headphone socket switch.
Bypassed this and radio functioned with serious low frequency 
audio oscillation minimised with bass at minimum . Due to sulphide 
corrosion between the wiper and track of the 200K preset on 
the power amp board. Removed the original hedphone socket 
and fitted chassis mount switched socket. To fill up gap in aluminium mount 
and the centralise and fix the bush used a push on circular circlip "wrong way 
round" teeth opened out and then fixed bush nut.
Beware of touching the back of the dial perspex when cleaning. The backing paint will rub off 
as easy as looking at it let alone getting cleaning fluid on it.

Morphy Richards Green Machine R166 windup solar radio
Slipping dynamo drive. 
The unused cog coaxial with a used one at the end of the brass 
spindle of the winder, cracked.
As unused bound up  and tightened around with wire and glue.

Nakamichi 730 Tuner Amp, 1984, 17 Kg
No powered control of volume and numerous front 
panel lamps blown, apparently no radio but actual fault of no stereo.
First problem - how to gain entry ?
Small cover at rear disguises screwdriver entry point to 
release (reverse sense of screwdriver) the chassis closure plate on the non-fin 
side. Then hex head bolts on fin side to remove top.
No hard power on / off switch , touch contact , unlabelled , 
at front powered by small transformer hidden under the main relay.
No motor drive to volume pots because of cracked track 
under pin 1 of CN-19 , the orange bunch, at the Tuner pcb.
Motors (at least volume anyway ) are 6V operation
Beware breaking contact of 330R resistor between this board 
and the ganged tuner means the motorised tuner knob 
bangs up to low f end of scale dial.
Just about enough room for ground down 5mm Green LEDs and 
390R droppers as a lower power illuminator or it is possible 
to put longer 14V bulbs angled so they fit the available 
recesses. Beware the common rail is positive. The 3 volume 
illuminator bulbs have plenty of space for larger or longer bulbs.
6V battery presumably powers the tuner pcb CMOS 4066 or function selects 
if unit totally disconnected from mains.
4 i/p select 4066 have rails of 10v,-10V 
and 6V and -6V control voltages.
As no Dolby logo on ICs the empty 10 way edge connector CN-1 probably 
held a Dolby board. Maybe because of its absence powering up with 
Dolby light lit then no FM throughput regardless of source on or off. 
With no Dolby board then deselct at front.
Voltages for receiver but for unrepaired lack of FM stereo.
Front panel lights set for power on,FM,Source, B (93MHz), 
Headphones load and 2 on volume scale.
ps +-58V then fuses 15.6,15.6V ac, 7.4V dc and red +12 and blue -12V dc
Tuning pcb connectors as numbered
Green, -12,0,-3.8,0
orange, 0,13.2,10,-12,12.9,0,12
red , 12,0,1.7,3.6,1.8,0,0,12,8.6,12,0,0.5,3.6
grey 0,16,-12,0,12,-0.4,1.2
preamp (numbering reverse sense)
yellow, 0.3,12,0.9,-6.3,-7,0.2
green -12,9.5,12,12,1.4,1.4,-6 to -9,1.4
blue -6 to -7,-6 to -8, -6 to -8,-6 to -8,0 ,-8 to -9,-8 to -9
orange 0,0,-6.5 to -7, -7.2,-7.3,-7.5,-6.7,16.2
CN-4 , 11.9,0,-12,-10.9,12,0.15
2way, 0,-11
brown 0.9,2.8,-12,0,12
CN3 , 12,0,-12,12,0,-12,0.3,16.3
Only about 5 mV of 19 KHz square wave on the uPC1161C IC pin9 
and no strereo audio o/p. Plenty of 19KHz pilot signal 50 to 100mV 
in the composite signal , choose to tune-in a talk station for clarity 
of the 19KHz component.
I seem to have accidently found a technique for handling stereo
problems on this receiver.
Disconnect pin 1 (5 ? not marked ) from housing in the violet CN-7 connector
that connects to upc1161 pin 9.
I looked at the DC voltages on the uPC1161, supply pin is
pin 1 at 11V but the pin 9 which connects to CN-7 was 12V
and the 12V coming from front panel , so thinking a fault on front
panel. When disconnected taking
this lead via 100R to ground then the stereo light comes on dim.
Anyway with this line disconnected the pin 9 signal jumps to
a 5V or so pk-pk PLL signal but rough triangular form and 2.2V dc
Now locked into 19.000 KHz over a good 20% of VR302 range 
and plenty of signal for a f counter to confirm.
With a screwdriver to inject hum at either end of VR303, hum
is either in L or R channel but without stereo lamp to
indicate, touch front contact and hum is central, L+R.
The tuning slug (nearest the 2 normal IF coils) buried in the 
Nakamichi IF block under cable bunch
needed adjusting slightly to bring up quadrature ? and the stereo decoding
and then
pin 9 dropping to .4V dc and 0.2V pk-pk square wave at PL in 
stereo condition at 19 KHz. 
Then reconnecting the CN-7 line these strong pin 9 ac signals
disappear and stereo light comes on. Balanced up the 3 pot cores
and VRs for minimum noise etc.
For insulation test of main large transformer make contact 
on the middle connection of the main relay.

Nytech CTA 252 XD about 1990,Bristol company
Blowing fuses and long term problem of tuned station drift
Firstly this is substantially different to the CTA 252 which has MC1310 (PLL)and CA3089 
(FM IF) but 
the ps pa and RF front end are probably the same. The same functions in the XO use a 
HA12003 and KB4420B . For general info the KB4420B 
is from Toko America which has a curious logo in a square perhaps a very stylised G C L 
the 
g looking like spectacles on end and the c as a hook hanging off the L. This chip is marked 
4420B and separately KR. 
The pass tranny mounted on the chassis labelled TR309 was BD??? unclear prbably 
BD507. Blown bulbs are CM159 wedge base 6.3V ,.3A. The front panel knobs in raster fashion are
P1 AFC CONT
P2 tape LO
P3 Mono HI
P4 SP1
FM SP2
phono power
The DIN socket on the rear is preamp out /power in and needs outer pins connected and 
inner pins connected to bridge .
When removing the front sloping panel leave all the switches fixed to 
the plate except the switch bank for the radio presets and lift the panel and edge sockets off the 
base from the meters end.  This assembly is a pig to reassemble - there are indirect edge connectors 
going in all directions. Remove the bottom plate so 
as to mark the indirect connector pins that go s/c on the switch action so on 
reassembly it is possible to check the sockets and pins are not misaligned. The set of 
contacts parallel to the meter bay is visible but not the intermediary boards in the centre. 
Ignoring the long preset bank of contacts, for the remaining long set the 2 endmost pins 
from mid-board end correspond to the nearest switch. On the shorter board pins 3 
and 4 from the mid board end correspond to the nearest switch. For 
working on the radio when disassemled with the top removed along with associated 3 indirectly 
connected boards disconnected there is enough signal feeding to the amp to work on the tuner.
One of the 63V 3300uF caps was shorted. Replaced both with 63V 2200uF because of 
space constraint. 
When reassembled there was serious fluctuation on the afc probably due to bad connections on the 
board interconnects and switch contacts. Cut the trace to the final afc point and 
soldered 1M to ground . This killed the afc so meant on initial switch on 
the preset station would be slightly detuned gradually tuning in as the unit warmed. 
Seemed too much effort to change all switches and berhaps ribbon cable all 
interboard contacts.
Theoretically it would be possible to up the top limit from 104MHz to 108MHz even 
if the meter scale is wrong.

Philips VC 600 car cassette/radio
No sound o/p in radio mode.
Components in different parts of the board electrically associated 
with the cassette in/out sensing switch affected.Although 40V rating small blue 
100uF electrolytic C2150 S/C and failed BC328 Q6078.

Pioneer SX 600L tuner-amp
Tuning drifting off station.
The function switch mechanism is divided into 2 blocks connected 
by a flexible slide way.The middle bank of contacts on the block nearest the 
front had poor contact affecting the tuning voltage.Melted the solder 
pin by pin pushing the pin with a small screwdriver and the slider(s) made 
good contact again

Pure Evoke 1XT DAB radio, 2004
Owner dropped it and now the volume control is very iffy.
Remove rear screws, internal front pair and remove the 
silly plastic reflex tube.
Desolder the aerial wires, ground wire, speaker wires, mark 
the connectors before removing.
Some screws hiding under flopped over electros and one under the daughter
board that has to be released to get to that one.  
The LCD ribbon connector
needs the closer pulling away 3mm towards the ribbon to release the ribbon.
It is a stereo resistive volume control with 4 concentric tracks 
not a rotary encoder. 
Desolder the LCD LED supply wires.
Vol control - Inner and next are conductive and the 2 outer 10K resistive  - of the 2
wipers , one connects tracks 1 and 4 and the other 2 and 3.
Marked B4 and B10K
Desoldered the 2 isolated mounting points to avoid desoldering the main 7
pins as they are sleeve/thru soldered ,
bending over and prizing/parting the 2 parts of the pot.
One of the 7 pins seems to be isolated from the tracks and i cannot see what
it would be connected to as 6 pins only are required.
It looks as though the dropping just slightly parted the metal clasp part,
holding the wiper and spindle, from the tracks part.
Bent back the wipers a bit and reassembled.
Uses TDA72669 m, 2x nE5532
Some DC voltages on connectors
Brown 5,0,0,3.3,0,0,5,5,5,5
near USB black 5,0,0,0,0,
black 2.9,3,0,0,0,
Exposed line of 22 contacts to the daughter board
2.1,2.2,3.3,3.3,3.3,2.2,var,var,var,var,var
0,3.3,3.3,2.2,0,0,0,0,0,0,5
I checked actual mains power consumption 
with the volume at minimum and it was 6W

Quad fm 2
Valve tuner and tranny stereo decoder.
Loss of stereo in high f part of band.
Replaced the second IF valve

Realistic DX  440 SW Receiver
Rotary fine tune knob so free to rotate that little 
more than breathing on the radio would alter the f.
Pushed a large diameter rubber O ring over the knob 
so it settled in recess at knob seat and against body of radio

Roadstar RC 611GD car radio
Intermittent channel.
Had been kneed in area of vol and balance control.
Broken balance pot but the real problem was the soldering 
points between the CD input socket daughter board and the 
rest of the front board.

Roberts R250, 1993/2003?
Sham retro Roberts radio. uses BA4424, BA4236, 2201X01
but seems genuine speaker from 1979.
Stopped working after changing battery. 
To gain access remove the 2 screws under the 
strap, remove back board, 1 internal screw for right side internal 
MDFB cheek and lever out both such end cheeks
Probably a fault with either the int/ext DC diverter 
switch or the on/off switch.
Packed out next to the looped sprung part of 
the diverter to add closure  force and wired in the second unused 
on/off switch. As this is int/ext capable and only 
diode protected for reverse powering, added a 160mA fuse in 
line to protect any ps.

Roberts R727 radio 1989
Worn volume pot
Undo base and push down the handle to release 
and expose 2 bolts
Uses TDA1904,KA2247 and a waxed in SILFM IC
Mark dial cord position and anchor off cord exit point 
from dial with cable tie- loose not rachet fixed before 
unscrewing dial pulley

Saisho portable tape / radio 
Non - standard telescopic aerial had broken 
at the pivot.
Remove all parts of the original and an adequate 
strong bond could be made by fitting the parts 
together,coating with flux,heating with 
a hot air gun and allowing solder to migrate into 
the brass casting.


Sony ICF111 rugged radio
Bad wave change switch.
Reconditioned as per tips file "reconditioning slide switches".
To get access to the track side of the pcb prize off the back face sheet of the tuning 
dial area,remove the speaker and cut away part of the plastic between the speaker surround 
and the dial indicator area. Anything to avoid desoldering all those wires and labelling and 
undoing/refixing the complex dial cord path in order to 
properly remove the plastic surrounding the rear of the pcb. Glueback  the cut away section 
when elecrically repaired. The silvered contacts at the end (open to air) of this slide 
switch were most tarnished so probably 30 years of airbourne acidity.

Sony ICF790
Intermittant loss of power.
Poor solder contacts between the mains inlet DC diverter 
switch and the main PCB

Sony ICF SW100 Walkman sized all band radio.
Clock and display but no radio display,function or audio O/P.
Dismantled all casing but not the LCD and its PCB remove vol knob and ferrite 
aerial leads and unclip end sockets cover
There are 2 .5mm spacing phenolic ribbon cables connecting the 2 PCBs through 
the display hinge an 18 and 16 way. On the 18way ways 15,16,17 were fractured 
so bridged these and ways 13,14 and 18 as a precaution. These cracks are barely 
visible.The thin side of plastic cracks then the copper fails. Pull back the retaining 
clips in the direction of the ribbon to disengage ribbon from the housings.
Repaired as described in tips file (repairing .5mm ribbon). Enlarged the slot 
these 2 ribbons pass through which required breaking open the hinge. The long 
pin at the speaker end unscrewed and then pulled out the other end.. On 
reassembly the on/off interpiece must be lodged under the tin(n)y switch lever.
The first attempt failed so redid the solder bridges and remounted the whole 
ribbon the other way round end for end. Beware one end the contacts are on the 
pcb side and the other end away from the pcb.

Sony ICF SW7600G scanning radio
Reported as bad power switch.Problem with the lock switch and ext power in.
Replaced the tiny push switch of the lock switch with a sub miniature button 
microswitch hot-melt glued into place. To extend the button used 2 lengths 
of nylon cable tie anchored away so they could bend between the cover 
mounted slide protrusion and the button of the microsw. Something wrong with 
the 4 pin dc power socket. Worked ok with batteries but plug in external 
and the unit would power down regardless of main power switch.
Reconfigured by  putting SM shottky diode in line with battery line to 
stop charging and conected the DC centre pin via SM 1N4001 to the 6Volt trace 
on the pcb. 3V or so retained on this unit to keep memory going for some time 
without 6V batteries but otherwise internal batteries are required for 
external powered function.
Identifying pinning marked on the main central staggered 
line of pins at centre of main board.

Sony MDX C150 car CD+tuner conversion from Japan to UK (+New Zealand)
Made for Japan use and FM band set to 76MHz to 90MHz, UK is
about 88 to 108 MHz
Monitoring the VT line to the tuner varies from 1.52V to 4.2V from end to
end of this band. 2 banks of 6 channels programmable in this 76 to 90 M
range plus 3 more that come up annunciated as 1ch with a VT  of 5.66V, 2ch
of 6.83V and 3ch of 8.04 V which coincides with a local station on 107.8MHz,
B+(for FM ) on the tuner  is 8.3V.
I changed the 7.2M crystal associated with the LC7216 PLL to a double PAL
frequency crystal of 8.867238M
and this brought the range up to almost ideal, a slightly lower frequency
would be better.
LCD reading of 80.0 gives a tuned in station on 96.1M and 89.5 on LCD gives
a station at 107.8MHz.
7.2M is used on LC7218 FM circuits so probably fairly generally applicable.
For anyone wanting to put an analogue tuning knob on a pot 
using regulated voltage of 8.3V at pin 8 of absent IC02 
then VT of 8.04V gives 107.8MHz
 and 4.21V gives 89M
Tuning voltage from LC7216 is pin 18 via FET ? Q2 marked G19

Sony TA F55 tuner
No function selection
Protection cicuit cutting in
due to failure of one of the front panel lamps

Sunny D 3x3
A load of gizmos but what were they ?
Ping-pong ball sized plastic spheres with basketball type patterning.
Socket for stereo earphones a switch Off/Lo/Hi , buttons marked seek and reset
Uses a 16 pin SM Philips TDA7088T. It is an FM radio , 
seek moves up band to next station and reset back to bottom of band, 
seems to be mono o/p.

Tandy/Realistic/RS PRO-35 scanning receiver
Audio and digital ok but no rf/if on some bands
Sanyo SIP IC LA1186 marked A1186 had been soldered
in skew at manufacture and at some point
a hair line crack of the encapsulation had
occured so replaced.


Teac AG 260 Tuner amp
No LCD display
One of the backlights had failed and for anyone else who can 
not find 2 6volt wire ended bulbs to replace with, use 6 LEDs 
in 2 banks of 3 serised together.

Technics ST 600L 
No display and no audio 
The relay signal from the LC 6512 was absent so the 12V line in the ps 
was not switched on.The fault was yet again insufficient soldering where 
mechanical integrity is required on the on/standby switch.This dry joint was 
not obvious and was missed on preliminary visual inspection and digital 
probing (poking around with fingers).

Technics ST Z35 tuner
No output on  any range
The muting contacts on the mains switch permanently in 
closed position rather than acting momentarily.

Tom-Tec WBR 902 cheap 'walkman' size radio
10 band fm/mw/sw uses 28 pin SM IC marked CHMC 53701 D1191
Battery compartment too tight to use AA Nicads and 
+ end too recessed for Ni-cads.
To open remove the Hi-Low button, screw under 
prop rest. Put screwdriver in strap hole and prize 
apart there and then all round. Pack out behind the 
+ terminal and with a craft knife cut through part 
where it meets body of the partial cylinder bit of plastic 
that surrounds the + end of the 'first' battery.

Vega 215 ,Selena Russian SW radio.
Poor tuning on some bands.
Sub-assemblies on the turret tuner had shifted (sprung 
loaded restraint) had dislodged after being dropped.


Diverse Devices,Southampton,England

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