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Repair Briefs - Audio Amplifers, CDs and Radios
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 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. Mains is 240V, UK.
Should the location of this file change please use the keyword "divdev7" in
a search engine to find it again
A number of the pictures are now apparently not downloadable, because the hosts have disallowed
remote linking although not saying so. To view them , you have to remove the picture file name
from the picture URL and put this .htm file name in its place
and scroll down to the relevant pic.
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 Alpha , 1985, Ser no 0022**
physically broken fuse carrier
TIP2955A, TIP3055A 2 pairs
4x .22R , 2x 330R
awkward variation of PK sc
rear panel long large inso sides
short large top h/s
long small 3 phono block
mid length small, 2 in middle area of rear
shortest small under h/s
Soldered in 2 replacement 20 mm fuse carriers
o/p layout , mirror images ea ch
Tx 18.2R//0.6R
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.
modified Arcam Alps switch/servo mechanism
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.
Audiolab 8000A
serial number just over 300000, 1983 so first year of production
Usual Audiolab connected series of 10 or more burnt/blown components, in one
channel plus other failures
This versions uses 2 x AL8AN and 2x
AL8AP each channel rather than the schematic I have, that uses 1 2SA1216 and
1 2SC2922, there are other differences.
Accidents waiting to happen , 3 E-line transistors per channel with bare Al
strip glued either side of the flats. One dropped off, 1 nearly dropped off
and the other 2 fell by just vaguely touching with a meter probe.
Replaced with 2 knotted rings of silicone sleeving
looped around with heat conductive paste and high temp
glue glooped over to make sure they don't fall away again.
Tie around the loops with small wedges between, slide of E-lines
and pull out wedges to put in place.
Another pointer ;-) to this amp being in the first 40 is the pots are
splined but the knob recesses are plain round, relying (or not in one case) on
the splines forming enough graunched plastic to hold.
Another noticeable thing about this amp being an early model. The pa power
rails are delivered by mains cable and I thought the green must be 0V. Then
I started hunting for the output lines to the relay and it is the green
wires.
The wires to the speaker terminals is also mains cable
Anyone familiar with the tendency of thse amps to ultrasonic oscillation. I
gave up on another one, years ago, because of unpredictable catastrophic
oscillation probably initiated by mains spikes.
The one I have here is the earliest manifestation than that schematic or
the one I failed to cure. This one had to replace about 12 components (half
of them burnt out) on one channel, other channel is probably good on this
one. Previous one was a load of burnt stuff in one channel also.
Removing the +/- rails from the bad channel and powering at about 1/3 of
normal , no load, then there is high level oscillation and high current draw
for a few seconds and then it disappears leaving working amp with a about
50mA quiescent draw.
Disconnecting that side and powering the ex-burnt channel the base voltages
of all the transistors now agree (mirror version) near enough with the good
channel. No oscillation with this channel but putting a DVM probe on the
base of the BC546B at the bottom of the schematic (with paired 1N4148 to
its emitter) will start the oscillation. Component values here are about a
factor of 2 different to that schematic,( 3.3V zener instead of 2x 4148 etc)
above but perhaps functionally much the same.
Touching the good channel one, after it has stabilised will induce the
oscillation also.
Hopefully just a function of running at reduced rail voltages . Other than
temporary adding some 10 ohm droppers in the 4 DC power rails for output
device protection any other ideas for ramping up to full mains power and
more importantly long term mod to reduce this propensity to oscillate ?
Reason for failure is not known , could have been piece of metal unglued
and adrift inside, but this could have occured while it was stored in a
loft. When I got it the metal happened to be in a safe spot of the good
channel. But it could have been due to 8000A oscillation, no abuse when it
was working.
Running up to full mains, the oscillation goes, I've not tried deliberately
inducing oscillation despite temporary droppers in place.
I'd not noticed, no decoupling caps across the 12 v zeners.
3x4k7 suggests quite a bit of current
too. As it stands there are no electrolytics at all in the power amp, the
100nF's at the 22 ohm main +/- rail droppers looks inadequate also.
Any thoughts on this as a failure mechanism.?
I've had to replace the +ve rail 10,000uF as it had obviously been leaking ,
probably for some time.
Maybe original was 50V, 10,000uF, just space for 63V one.
I assume in those circumstances, in use, hum ac
increases and the +DC rail decreases. I know from powering at +/- 15V the
amp oscillates. Perhaps -44V/+20V or so, it also oscillates, hence
catastrophic failure, but would one expect one channel oscillating to set
the other one off too. ?
I did not think the loose metal plate was the cause, as not the slightest
"spot weld" mark or smoke staining from a nearby immolation.
I added 47uF over each of the 4x 12V zeners.
Electros over the 12V zeners looks like a generic cure, decades late, for
all audiolab ultrasionic oscillation. I returned to variac powering giving
+/-15V rails and no startup oscillation or initiating from touching that
transistor base.
1 meg Rs near relay for monitoring output and feeding back via IC1
Mains transformer 7.2R/<>0.1,0.1R
phones droppers 330R
22K between + and - 3.3V zeners instead of 2x 4148
With reduced power +/-15 to the +/-44V rails and
good channel nearest relay, 15 R droppers in line with
the power rails
measuring bases of TO220s and centre pin (base) of others
forewards in lines (other channel nearly a mirror)
-14.7,-14.7,14.7,14.7
-.6,-0.04, -.5, -.5, -.5, 0.04,.67
-1.1, 1.1
-12.9, -14<>-15 (probe touching starts oscillation), 10<>12, 11.7
zeners -15,-13, 12, 14.5
-3.2,.96
-3.2, -2.6, .9
zeners -4,0, 0,3, -4,-.5
6 sort of line -.5,0,0,.9,1.5,1.6
With replaced components in other amp
the reduced quiescent voltages agreed with these ones
so took the rail voltages up
burnt Rs 510, 47, 220,220,330, doubled 0.2R at output
BC546C replaced with BC449
o/p devices replaced with TIP41C,TIP42C
ZTX753 replaced with same, MPSA92 likewise
Considering tuner i/p , lines go across the front
to bal and vol and return to 4.7uF,50V
then Q1,Q2 between REC and Bass controls
prea o/p at Q16,Q17, useful monitor point
junction of 560R/10R in middle of board
prea-pa junction
Q19,Q20 local ps
With full rail voltages and both amps working
400Hz 0.05V at tuner i/p , 32mV at the prea-pa
juncture and 0.85V at output, no load added.
Audiolab 8000A amp , 1984
beware requires prea/ pa interconnect links
protection/ op relay cct falsely cutting out after an hour
or so
Would seem to monitor the junction of 2 resistors fed from each channel
output.
Pink, Rch, 47K
Purple, Lch, 56K
Why unequal? all inside looks original
The pair of 1M resistors off the outputs are feedback into the amps via IC1
Yamaha uses different value sensing
resistors so that in the unlikely event of opposite DC offsets at both amp
channels' outputs, the protection circuit won't be "fooled".
If you had +X volts at one amp output, and -X volts at the other, the
protection circuit would not trigger, and you'd have two blown speakers.
With this amp +/-44V so 4Vdc maximum available in that worse case, 3.1V if
following impedance is 100K and still 1.1V if 10K impedance
protect cct Q9 to Q16 , centre pin voltages in normal speakers on mode
Q9 -.3,10 43V,11 0, 12 0 , 13 -.1, 14 13V, 15 41, 16 36V
Anode of relay back emf relay , trace goes via phones socket
ground switch which showed >10 ohms corrossion at the switch.
No obvious route as under the mains transformer.
Added 4x 22uF,25V caps , 1 over each 12V zener as in other tip here,
to avoid "fridge" dV/dt ultrasonic oscillation and failure
Load testm with top cover off but under plate on
, vol set mid (vertical index), mid bal, mid tones
400Hz, .17V at both tuner i/p ch gave 4.6V ac over 8R and
with thermometer bulb over the h/s between 1 pair of o/p devices
and stem over the rear of the amp, 12 minutes to plateau at
40 deg C over ambient.
Audiolab 8000A trips out on a bass note using the amp at about 60 percent
volume.
Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - wrt
ground either channel.
Is 4V trigger level too low for some sorts of music and or speaker
inductance effects. ?There is some integration/standoff time , maybe
shortens with higher detected voltage. At 4.5V it is about 1/2 second before
relay clicks over, but 4V corresponds to only 2Watt of DC power
http://sound.westhost.com/project33.htm
mentions
"The detector circuit shown in Figure 1 (1) is simple and works well, and as
shown will not trigger with a 30V RMS signal at 5Hz, but operates in 60ms
with 30V DC applied, and in 50mS with a 45V DC supply. This should be
sufficient for most applications, and allows the use of a non-polarised
electrolytic capacitor in the filter. "
well above 3.5 to 4.5 V dc fault trigger levels
This Audiolab, unfortunately, has the track side of the protection cct
mainly covered by ironwork supporting the transformer. But as far as I can
trace out, it has 3 Tr like that Trace cct alluded to before, but 2 100uF
standard electrolytics downstream of the trs
back to back for unpolarised. I'm wondering what to put in there to keep the DC
protection but reduce the efect of 10Hz or so high level ac tripping
Eventually ground back part of the obscuring plate to see this area clearly,
leave a spot weld for the pot bracing.
pa schematic out there but not prea it would seem. Preamp
problem t'would seem. At switch on a pair of 47uF electros fed via 120K from
27V rail give increasing voltage that at about 8V , after 4 seconds, ends up
putting a 3 to 5V pulse on the preamp outputs , straight into the power amp,
both channels. This timed hold-off would seem deliberate, presumably muting
off, but the DC surge?.
Anyway this of course upsets the amp which then has to re-settle, otherwise
seetles in first second , but now outside its own time-off period and delays
relay turn on ,or worse , makes the relay chatter , via its DC loudspeaker
protection cct activating.
What to look for that the preamps , both channels oddly, come out of mute
with a surge ?
As 2 separate "timers" I will add another 120K to one and see if the effect
is the same 2 sec in and 4 sec in.
As it stands they time in near enough together but only one may be at fault
and cross coupled into the other channel, otherwise 2 separate but identical
faults seems iffy. It may be a hf oscillation problem .
When I was scoping the amp output there was short bursts of 150KHz or so at
this 4 second point. Did not think of scoping the preamp then to see if the
hf was there also or just the DC pulse.
no FETs in there BC550 and BC560
only.
Is there any recognised circuit supplemental to allow for the replacement
transistors going leaky over time?
I suppose 20 years before metalisation creep/migration re-occurs in the
replacement, is fair use.
Response time of relay trigger for 3.9V on 56K/47K junction , less than 0.1s
Time with 50K dropper to that point and 3.9V on end then about .5 s
Changed most of following, wiorked , but continuing problems , changed
back to originals
Q11.Q12,Q16, Q13 BC546BP to BC449 rotated
Q15 changed
Q14 BC556BP to rotated BC556
26V mains AC at Q13 via 10K
In operation dvm on Q14 base rises t 7V , not enough to trigger
relay then remove and after a couple of seconds. Reapply DVM and
measures 14V and drops to about 12V and relay drops out.
44V via 100K to 21.5V stable, marked 100K clearly on overlay
charges to 12V and wavers and relay chatters on and off then
goes on and continues up to 21.5V.
All 3 100uF caps measured same good ESR.
Red/green twisted pair passes 44V from main ps end, via the sub-front, to the double
pair of BD135 and BD136 that gets hot on the other end.
27.4V and 5.8V at the large caps near those BD...
no FETs in there BC550 and BC560
only.
DC pulse in the prea , not oscillation. Both channels the same , by
changing one to 2 sec timing in.
Using the eservice 8000C preamp schematic (bottom right splodge) as just
litterally a pattern and then following traces and filling in component
values, the stage around the 4 sec timer and nearby circuitry agrees with
the prea section of this 8000A.
Other than the pulse starting from a Q13 with its base at a zener 4.7V at
switch on and after 4 seconds turning on , will have to see why a jump and
not smooth , but design would seem to be for a step change.
As I cannot find anything wrong as far as broken wrong, I will assume this
is as designed. I cannot see why there is a low 4K7 dropper from 27V to the
4.7V zener that basically causes this 5V DC pulse, when only supplying 80uA
at most into the base of a TO92 transistor, Q13. I will try upping the
dropper and adding a C to give a time constant of 2 seconds and change the
main hold off time constant from 4 sec to 2 sec also but keeping 13V bias
point, both channels. A few strange noises in the first couple of seconds ,
if that and only if the phones are connected, is surely preferable to 5V DC
pulses fed , delayed, into the PA.
So both will rise approximately together and so no 5V surge is possible.
Q1 and Q2 rise smoothly
Q3 and Q4 base jumps after reaching .5V to 4V
Q13 base goes to 4.7V immediately, collector jumps from 4.1V to 5V after 4S
and then rises.
Testing with simulated bass input using 50mS Wavetek function gen ,
2Hz, 50mS pulse 2V pk-pk
-1.38V to -1.28V on Fluke DC, 2.6V pk-pk
Changed relay timer 100uF to 50uF still relay clatter
47K/56K junction -.5 to -1V on pink and purple outputs
Ground 560Rs between prea and pa and pa zeros well.
Temp changed each 4148 diverter Ds at the DC relay cct
to a pair of 4148
No change in sensitivity , grounding centre of negaive ones
proved problem on neg side.
Probably a chemical derived DC off set in the 100uf giving a few 100
mV of DC
, replaced with 2 more back to back , although ESR and capacity
of originals was fine.
.4V pk-pk at tuner and 200R instead of 100R
at 2.7K/100R on both channels
20mS pulsesstart to down turn period 400mS.
10V pk-pk measured on 8R o/p, temp rise both channels
Fluke 77 on analogue scale peaking 150mV on 300mV range at 47K/56K point.
Temp of heatsink rose 24 deg C over ambient with both top
and bottom covers off. Leaving volume setting and temp drops to
9 deg C over ambient
Dropped the 200Rs back to 100Rs
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.
Cambridge Soundworks Desktop Theater, DTT2200, 5.1 channels, 2001
other numbers on the chassis EAX CSW 4300
Loss of front right channel, after all this may be have just been
ring on 3.5mm plug being either too small to make at sockets
or break the diverter sw.
First thing to do is swap front and rear leads around to see if
problem swaps speaker or stays the same.
Try a 3.5mm stereo extender socket to plug also
Tip is L ch, ring is R ch
Internal speaker 3.7R
TDA7372A and 2x Creative CT1975, 5 x TL072, 4x M51132L (incidently
the M51131L looks identical via the datasheets)
No info found on these Creative 11 pin audio output devices except
"Creative used these amplifiers in the previous generation speaker systems,
like FPS-1000 and FPS-1500."
Nothing found amiss ,cold, via DVM for all 3 hybrids
For 2 known good CT1975 , DC V, no load
pins 1 to 11
0.8(ch2 in), *, 0,8,0.8(ch1 in),0(gnd),8,8(op1),16 (sup), 8(op2),12.3
* is 2 V on one used as 2 separate channels
and varies (no pcb connection to that pin) 0 to 0.6V floating presumably, on
one probably set in bridge configuration driving the sub-woofer.
pin11 is standby
pin3 connected to ground
any guesses on the next 2
p7
in normal amp 100uF cap to ground
subwoofer amp 220nF to ground
p2 on the CT1975 where there is a connection to p2
100K to ground and also to the base of a TO92 via an r.
TDA L&R
8.1,8.2,16,1.6,1.6,9,12.3,0,0,16,1.6,1.6,16,8.2,8.2V
pin 5 sig in and 20 out but not on the other channel
transpired , not used , to confuse matters
"umbilical" front to main pcb interconnect (B=Back/rear, F = front, C = centre)
pin 1 at front
p1 CR,2CL,5Bl,7Fl,9Br, ,11 Fr
TDA p2 CL, 14 BR, 15 BL, fourth ch not used
Front remote control and lead checked out ok
pins 1,2,3,4,5,6
swap to 3,4,2,5,1,6 on inside
If pinning on the mini-din is 1 to 6
vol 1,2,3,
bal, 3,4,5,
LED 6
on/off 1,4
Load test on CT1975, one ch
Max vol, mid bal
0.045V ac 400Hz in , 1.25V at speaker 8R
.125V at CT1975 i/p and 0.045V at "umbilical".
If a TDA.... etc is placed in place of 1 or both channels
in a CT1975 , and the replacement TDA has no standby/mute the relevant M51132
may have unused mute function.
Mission Cyrus one, 1986, ser no 1128..C
CEN C 86 04 on pcb and 85/86 on chippery, 8609 ink stamped on pcb
loss of one channel due to failed vol pot Alps 537P 10KWX22x lin 10K , only
held to the board by a piece of copper wire soldered to pcb and around the bush.
So when removing the front panel and 3 shaft extenders, hold this vol pot
or likely to break the paxolin if the metal pot shaft has binded to the plastic extender.
Failure was probably from being dropped as the 3 under fixing points were broken
but as plastic maybe inevitable without abuse.
Replaced with 2x 20K log pot with a mounting plate, enlarging pcb holes to take it
and 10K over the high ohm ends to wipers to give good enough approximation to linear.
pa side like the 1999 Cyrus 2
400Hz 8mV with vol at 2 gave 95mV (misnoted as eith R43 or op)
PT7 op tr ==BUV28 in passing
The mounting screws for all the PT7 needed tightening.
The phono sockets are not too brilliant and corrossion on both selector
switches up to as much as 100R but resolved with electrolube
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.
Exposure VIII (Exposure 8) , 1988
One channel died for no apparent reason
Looking at a www pic before attacking, this amp has black
painted Al casing that the exposed edges are easily chipped off
EXP8P allway shorted N ok and burnt out R26 68R , R17 `100R and o/c 2W .22R R31
Replaced EXPs with MJ15023/ MJ15024
Also uses SM2178A, SM2177A
2W 0.22R and 6.8R
1 channel DC, no speaker load
TO3 -41.1,0,-41.6//41.2,0,41.6
TO220 -.9,-41.1,-.3 // .9, 41.1, 0,3
thermal TO92 -.9, -.2, 0.6V dc
Load testing done with each amp in turn , just the L plate
disconnected from chassis and tied vertically with thermometer
laying in groove between L and pcb.
Both amps much the same result, one amp
0.166 V ac , 400Hz in and initially 4.04V ac out over 4R
Took 15 minutes to plateau 47 deg C over ambient and 4.04 drop to 3.99V
Goodmans GMR9500S , 1999? wifi speakers
Pulled on the floor and vol pot stove in
TDA1905
pots marked A5 03 FJ, log 50K.
Replacement , larger bush nutted, wired in and made hole through case further up, blanked off original
hole with a disc of blue hotmelt rod.
If gnd points of pot are not cross linked then max vol only
Used 10K linear replacements, perfectly adequarte
Harman Kardon AVR30, 1993
no vo/p or phones
4+3 fuses ok, relay click noise
An odd fault, no audio out as though in mute mode. The user manual says if in mute the volume knob LED
flashes. What LED, nothing lit, just the power LED and function LEDs.
The 2 thin wires that loop around the rotating pot motor shaft must have snagged somewhere and tugged
enough to bend up the pcb connector socket and break a wire somewhere. If no LED load , the amp goes into
protect/mute? the next time the amp is powered up, but caries on as normal until put in standby.
check knob LED on a bench ps
Wire ok, plastic header socket should be vertical to pcb, but being pulled over , levered
the pins through the housing, leaving little or no contact to the pins
Balance pot so bad that only one ch reliably.
Remove "back plane" behind pots, pulls off main board headers.
Mark the ribbons before removing
Remove pot nuts including sp sw nut. Just about enough loom length to
bring pot board through gap at the top
pot ALPS So906503-50KMN 330r Japan
Comes apart easily enough to renovate.
Returned soon after with front left o/p bad , also on phones,
farty noise then low level or nothing, all inputs.
When bad it is half-wave
problem near W1502 conn if pushed down but not conn problem. Actually the high current Qs
where the pcb phenolic is discoloured from heat and bad solder,
Q416 +1 and Q413 +1 . One of each pair is zero ohm EBC in CD mode anyway.
Also 2 of the 3 TO220 on the ps Al plate , bad solder.
4 top sc to remove "backplane", 4 +1 long central sc and numerous
cable ties to swing up the ps board. Undo 4sc of the mains Tx
for some more room. Beware of weak unsupported phenolic boards
on this Tx, I broke a part with 2 fuses on and had to wire-bridge back in place. Unclip gnd/IR/5V lead
Q6, and Q10 bad,Q8 ok, glue the Al plate back to the caps before resoldering.
Reassembly get corner of ps pcb under the mains sw first
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. Packed out the standoffs 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.
JVC VN 900, 1973 amp
Noisy vol control then problems on one channel.
With the top retainers removed from over each pair of sub-boards
make sure some insulation between boards and pillars before
powering up.
circuit designation STV-3, probably a triple diode
for bias seting. Parts listing absent from the manual, just
68C on black body 4x7x10mm that looks like a slotted opto device but instead
of square bottomed notch , semicircle curved, for bolting down, but mounted on pcb here.
Just found a side ref to it in the manual, a varistor, part number
E03094-002
circuit symbol 3 triangles in a row, like 3 diodes without 2 of the cathode
bars,
not skew Z over a resistor, or back to back triangles
Probably varistor diode but no useful data found yet , whether varistor or 3
diodes or varistor and 1 diode or whatever, or that symbol found elsewhere
I was taking 6303 on the Elno main caps as datecode , dark brown phenolic
pcb board, wire-wrap type wiring and some strange transistor packagings as
being consistent with 1963 but will burrow again
Not that 150A package but
Imax 120mA, Vr max 50V, Ir max 10uA, and at 7mA, 1.65V forward V, -7mV per
degree C
As one 1n4148 is about -1.6mV per deg C then 3 in series would be about
right forward V but not enough thermal response at -4.8mV , is Ge more
thermally responsive ? or some sort of NTC thermistor in there as well
1N4148 at 7mA would be more like -2.3mA per deg C so 3 x 1n4148 looks
suitable. These ones measured 1.36V DVM diode test in cct
No other datecodes found, so presumably ELNA QEY 6303 is a type number for
6800uF 63V electros.
Light grey cement/epoxy? cased resistors are more 70s than 60s
Some strange-to-me 2SC960 bolt-downable (but not here, like the varistors)
packages , different to my 1977 databook listing, but all types in here are
Si not 60s Ge
Presumably about 1973 made, from www cites, although I can find no indicator
inside the amp.
Can't find 6303 as an ELNA type number , so maybe old stock caps used.
Those 2SC960 with great bolt down mounting flanges, that are not bolted,
floating in mid air look mighty strange also , no package pic/type number
found for them, somewhere between TO3 and TO37 but flanges twice as thick
but TO5 size cap .
Amp serial number 046017**
This VN900 originally had sun damage rack and pinion pivot switch (pink
noise sw), metal actuating pin heated up relative to plastic and cracked the
plastic. Also worn pot. They went to a High St repairer and a 2SD188 went
C-E short on one channel on initial powerup and they gave up, the 2SA627
went o/c.
And for good measure had coffee poured into it, in its very distant past,
when the owner was a student.
Have ground off the pivot rivet and got the switch dissassembled, metal
ground down a bit to give some slack and hopefully capillary superglued back
as one. Will probably replace o/p pair with 2955/3055 before wasting
anything more contemporaneous.
Placed switch pivot in a plastic bag and glue passed 1lb load on end of pin.
Next the vol control, quad ganged pot with bass comp CTs, not many of them
around no doubt. To disassemble requires grinding off the swaging on the end
of the shaft, presumably drill + maybe tap for screw and pad/washer to
refit. VR7,8,9,10 250K, BX4 , E03413-002. Beware dedent ball inside
rear cap. Holes in individual covers may allow thin nose
artery forceps in there to deflect out and down. Added graphited
silicone paste to good effect.
A grey small electro on the main board has perhaps leaked at some time
SEA (punningly in blue print on front) stands for Sound Effects Amplifier ,
from the user manual, me thinking Selective Equalisation Adjustment
so far not broken an age-hardened hookup wire.
Easier to work on than a lot of 70s stuff, can remove sw and pots etc with
room to manoeuvre, wired in place. And the edge-connectored multiple cards
makes it a lot easier, presumably can swap between channels for diagnostic
purposes if required.
All the nuts for the VN 900 ,TO3 were loose, not to point of dropping off ,
but not as tight as I would expect, so worth checking your one, compressed
nylon insulator/spacers?. Sw rebuilt , quad pot graphited paste pushed in
for the moment, won't know whether requires rebuilding until I can get some
power on it.
+74V DC rail to a preamp , producing low current shot noise?
Particularly the third transistor in,
250V rating 2SC1103 and associated Rs would be my guess at noise source.
I put some manky oily residue (not all over) down to a leaky nearby cap ,
replaced , but tested ok.
Perhaps a breakdown product of that dark phenolic 60s type pcb, like "dolls
disease" in soft plastics. I'm wondering if the SEA board , populated with
70s Si Tr and Rs &cs ,along with the main caps, is a hang over from earlier
60s model.
mains tx prim 7.3R
thermistors on TO3 h/s 163R NTC
C337 replaced with 10u 50v
Graphic transformers E03108-17B 630/180R in cct
-18B 650/64R in cct
87/23/16 others
Replaced L ch o/p TO3 with 2955 and 3055 powered up ok but over a certain
level of signal the relay/protect cut in and out and also this
new pair of o/p heated up. Innermost large heatsink corresponds to driver
board nearest front of amp.
Relevant R423 had migrated from 220 R to 330R.
Replaced and less heating at op but protect problem remained
and X406 ,2SA607M associated with that 220R was heating up
replaced the pair of drivers with TIP31C and TIP47 (i know not strictly
comp pair) plus some expanded Al mesh pieces for heatsinks.
DCV measured with 5/6 mains voltage , no op loads, on pins numbered 1 to 18 on driver board.
Original and replacement channels , with no signal throughput , so no
relay problem, measured about the same
p1 -.2,p2 0,p3 35.5, p4 .5, p8 0, p9 -.7, p10 -35.8, p13 -14.5 V
Then one channel,R, was obviously noisey. Due to the first
transistor in the S.E.A filter. Swapping predriver
boards around, same ch problem. Temp rewiring, crossed over, the
outputs of the preamp board , same channel.
Shorting the base of the final SEA transistor to ground
stopped the noise but the first one was the problem
Replaced X301 and X302 of each channel with leg-twisted BC547.
Added grommets around the separator /top-clamp pillars
for all the double board assemblies to avoid shorts to the pillars.
Switching in System-1 speakers would cause current surge of the mains,
The cable between front sw and rear pannel went under the power
transformer bracket and the bottom pannel screw had punctured it leaving one
filament of wire touching chassis when screw was removed.
R ch noise. Swapping predriver
boards around, same ch problem. Temp rewiring, crossed over, the
outputs of the preamp board at 470R , same channel noisey.
Shorting the base of the final third SEA filter transistor X305 to ground
stopped the noise but the first one was the problem
Replaced X301 and X302 of each channel with leg-twisted BC547, BC549C.
Added grommets to the pillars dividing boards to protect from shorts
while top clamps removed.
o/p check on 8R load, R ch (nearest edge of chassis pa heatsink)
2 upper sw buttons out , lower pair in, levers horizontal
400Hz 1V sine in , 6V over 8R and 14 minutes for heatsink to rise 41 deg C over ambient
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
Marantz PM 66SE , domestic amp of 1996
Protection circuit relay fails to click over, because no 24V rail.
I was told someone has previously had a look. R801 and R802 are droppers in
series from the 44V main rail down to a 24V rail TO220 pass transistor.
R801 looks genuine 1R 1/2W, but R802 has the wrong lead bending (none) and
different colour banding structure to other Rs on board and measures 4.7K,
1/3W which makes no sense and just a couple of volts at the pass transistor.
Replacing 4.7K with 220R the 24V relay clicks over etc
Dropped voltage at the 2SC4883 is 32V for first few seconds then drops to
24.8V on big relay activation. So about 1.8W dropped over "R802"
"24V" rail drops from 23.2V to 22.8V
Going down to 110R then 37.1V to 32.8V and "24V" from 23.7V to 23.6V. About
1.1W dropped over "R802"
Assuming the original was yellow green something what was the likely value
resistance and wattage of presumably fusible resistor in series with the 1
ohm ?
A lot of the red and orange colour bands on other resistors have faded to
brown and silver/gold bands have faded to feint
Replaced it with a 1W 47R in series with a 200mA fuse. 24V rail is 24.1V
with or without the large relay being powered and about 5V over the 47R.
It makes more sense to be the other way round , 1R of .5W and
47R of 1W, apart from seriesing 1 and 47 ohm.
100mA for one 24V large relay , 2 small 24V relays plus some circuitry seems
reasonable. The heating of the, heatsink-less, pass transistor is the same
as the one for the -18V supply so again seems reasonable current.
So 0.5W dissipated in a 0.5W resistor is questionable. Hopefully a 200mA
fuse and larger 47R makes more sense.
One or two small relays click over at switch on and then the main relay.
Uses 2SA1266, 2SC3182 darlington 2SD1508 ,AN7062 and TA7317
Q801 24V, Q802 -18V. Small dughter board 5V regulator has 34V supply
which is dangerously close to 35V limit for 78M05.
If the phones switch goes o/c then mute would activate.
Beware, remove the main switch extender before dismantling front pannel
as very frail plastic interconnects
Apparently R801 is the same as R803. R802 is the same as R804.
Balance would seem to work only with tape in/out not normal
amplifier use.
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 2SD669A 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 3040
With no input, crackle on L ch , even showing on meter.
Killed by turning balance to R ch fully.
Vertical daughter board nearest front was the problem area.
Changed Q401 and C401 as vibration sensitive , but
so was same area of the R ch.
Probably solder problem between daughter
and mother board, extended out to check.
Pin 3 21.3V, pin 6 -22.3V on this interconnect.
4x 3055 , BD139, BD140
6.3V ac on meter bulbs
main +/- 31V
8.7K/45K turning balance and pin 5
Poor ground on larges circle pad on main board.
BC549B, BC559B, 2x BC556A, BC546B, BC558
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 contacts to 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 pin din. But connect CXA to CTA via the cross-over
type 5 wire 5 pin din 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
Realistic MPA 100, 1992
Worn out thread on output socket. Added banana plugs
to speaker leads
Uses 4x10R, 4x 100 A1306, C3298
C2229, A949
12x .2R, 2x 560 27K, LC1237
Returned years later for drop in level of one chanel and flickering meter lamp
lamp flicker , bad solder on other meter
Iffy solder on 220R of amp into reinforced solder run of a rail on the ps but likely problem
was trelaxed spring of metal to spades of speaker terminals, plenty of wire length to
snip off and solder on, remove the amp to get space.
"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
Roksan Kandy LIII amp , 2007
Owner has seen this thread
http://community.whathifi.com/forums/t/313192.aspx
and would rather I looked at it rather than the maker
Easy to blame PbF as printed all over as such.
Problem is different to that above thread. For ages now the R ch has failed
occassionally at switch on. Switch off and most of the time it comes up.
Very rarely that ch dies in use, Then last week both ch failed at sw on , so
he decided something needed doing
16 amp output relays
Make Finder 40.615 , clear cased so can see the contact gaps
About .75mm for the R one and .5mm or so for the L. Thinking fine contact
contamination and not enough mechanical punch-through.
Both relays in series from one supply and TA3717 ptotector IC
Or any other ideas other than checking phones socket, if wired in to affect
output somehow, PbF solder looks fine. Wanging with engraver and nylon bolt
has only highlighted a microphonic capacitor.
Looks like another amp where I'll make an LED mod that the owner can view
through the phones socket. Bring out pcb mounted, relays-on LED ,and add a
different colour one for the main rails supplies on, both viewable through
the phones socket transparent plastic panel at its rear
Got the combined phones socket and motorised vol pot board removed now.
Phones uses switched ground contact for cutting speaker output , via relays,
so not a
suspect now. Can see why there are "pot" problems with these amps but not
this one - YET. The PbF soldering on this board looks terrible compared to
main board , no chance of the "green ring" of concave sided volcano mirror
PbF finish here under a 30x . Matt grey crystalline and cracking solder so
the "ring crack" of PbF likely in a few years with normal localised user
induced vibration from using phones or turning the vol knob.
Used wide cable tie (in tips) to remove the vol knob
Another problem with this amp. a small DPST 5V relay switches in minor
+/-15V rails but one pole contacts welded closed. Supply side cap 220uF/
25V and switched line has 68uF/35V (replaced with 22uF/50V which is blown on the permanent welded
set of contacts, other rail ok so far. There is 000 ohm resistor down stream
of each contact , contacts are 1 amp DC rated and is
probably just supplying 4 dual opamps and no transistors or anything else
active in the phono preamp and tape-in and tape out section. Replaced R42? and R42? ,2x 0R with
2x 6R8 SMR in each rail to limit switch on current. Presumably all
those , user unused , opamps were permanently "powered" unipolar, never
checked phono inputs on initial testing
2x24V relays in series +390R off main + rail
Phones 5 wire , R wire grounded normally and open with phones plug inserted
goes to R718 and Q702 , Q701 near the TA7317 , bad solder on p6
Relay Ry 109 permanent s/c contact
6 caps bulging C440 blown and erupting off white electrolyte
C431 TEAPO SY105 deg C and its match replaced ,
C236 and C238 SN 105 deg C
220uF/35V with 220uF /40V
5 long sc are at the phono bank
Don't trap speaker wires under H/S or jammed against pcb pillars.
Large after-design butchered milling relieving for the phones socket at rear of front panel Al.
L-ch TOP66 and TO220 with 270R load
-1.6,-54.4, 0 // -2.2,-54,0
2.4,53.5,1.8 // 1.8,54.4,0
Need pcb ground screw in place at rainbow ribbon
44V on both relays, 2x8 amp parallel contacts maybe better than 1x16A.
Hole to side melted thru casing , using .45mm Teepee to clean
and closed hole with hot mellt.
Out of chassis connect a plate across the 2 unsupported heatsinks.
PS area ULN2804A, TA7317P (protection) ,7812, 7805
2W 120, 390, 10K
Prea 7815, 7915, 4x 5532, 9 relays
PA ea ch
2x 2xR22, 390R, 2x 5K1, 2x 2x R12, 2x K1529, 2x J5200
1 power o/p relar, 1/2 N5532, C4793, A1837
Motor control BA6218
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 RA1312
phono 2 i/p ok but phono 1 , rt only
Bad funcrtion sw and also poor rotary mode sw
Function switch, interlinked S/R ganged switch, 5 gang, each of 4 pole 2 way
with pins extending above and below and a pcb above and below . One failed
switch contact. I'm surprised I've never had to break into one before,
serious miultiway radio waveband switches , yes, but they are not ganged.
This make of logo TMS in an elipse, hopefully applicable to other makes of
ganged switches.
How to get inside without desoldering all that lot.
U channel steel between the 5 gangs has 4 nibs , bent over, to trap each
gang , bend back those 4 and the next 4 along the gang strip to give some
lee-way. Small blade between that channel and the sw body to lever and give
enough gap to release the S/R interlink that runs inside the U channel , and
in this one release a nylon limit widget , from under the spring and then
the core of the gang simply slides out. In this case aged/compacted grease
had wedged the phosphor-bronze contact away from ever making contact.
Qtip and meths rodding the core, and soaking of the other parts
to totally clean off.
I tried opening a more recent ALPS multi-gang switch, laying around, with
pins emerging top
and bottom. Much the same routine to extract the core , no ball bearings or
anything other than the contacts are likely to drop out. Easier to
reassemble than those long radio waveband switches, lay the innermost pair
of contacts in their wells, push in, then add the next pair and push in.
On the TMS ganged switch ,inner pair of contacts ok, but only one was making
for the pair nearest the front panel.
To check the rear mounted phono amp sw etc, 2 sc either side, 3 large sc under and 4 sc 1inch up
on the rear plate.
To remove the front , remove bottom cover , top screws, knobs , balance skirt
comes off with the front panel, 4sc under.
Mode sw spray contact fluid from under
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.
Sherwood RD6106 tuner amp, may 2000 from front panel moulding
I though that hygroscopic brown glue stuff went out in the 70s. Used to
secure 12.288M crystal for the digital interface processor YSS912C-F , was around its
pin and had rusted through at the epoxy bond. Plenty of opportunity for
liquid to pass through top vents but no sign of liquid anywhere so
presumably this duff glue stuff again. Luckily easily replaced.
Unfortunately looks as thogh it was used as flip-chip temporary bonding
before soldering, hopefully away from anything rustable there.
CP801 resoldered , CLK end, if plug lifted from that end to break contact
then loss of signal throughput of radio
Phones socket mounting broken , hot melt glued back. Easy to replace if
necessary as simple non switched L,R and common lines and 4th is just some local screening
main rails +/-42.7V no load
With .25V 400Hz in at vol 70 both ch FL/FR/SW at 0 in CD mode , cinema Eq off
9.6V over 8R just the 2 main ch and +/-40.2V DC rails
With thermometer bulb at Tr end and stem laid across the top of the h/s and no top lid
took about 15 minutes to stabilise at 36 deg C over ambient
4x 0.22,6x 10R, 2x 470,
DC on ribbon in CD mode
0,0,0,0,0,43,43,43,42.7,0
0,0,-43,-43,-43,0,0,0,0
in 6ch i/p mode
0.089V ac 400Hz , 3.3 to 3.5V ac over 5 x 8R loads for 2xF, 2xR and C
presets at 0
Sony MHC 901av , 1995
phones output but no speakers
That is 3 pairs of speaker outputs, CD,tuner and tapes ok. Left unused for a
few years.
Will check for amp noise on the speaker outlets in the next hour. At the
moment I'm thinking muting via corroded erroneous phones bypass switch ,
impossible to see /probe without taking all apart. Any other ideas to look
at. Looks like 2 stereo SIP hybrid amp packages, unlikely both failed, no
approprieate fuses seen yet.
Now found a pair of relays that had no sound of click-over, but monitorable
for signal and control, assuming a minimum number of board interconnects is
enough to test out. Managed to get to the phones socket and the isolated C/O
sw is fine (or I disturbed it), but at least I now know which lines from
there go to the relay board and the output lines from the 2x STK4142II .
noise from relays at switch on as insufficient current or something so a buzzing noise,
until they click over - left as is rather than spending even more time on this
Unclip CD top clamp to clean lens. slide out drawer , slide rearwards the deck
to unclip from underlting metal plate.
Unclip the large standoff from the pcb and keep with this steel plate.
Uner the tape section 5 sc to remove lower steel frame with the 2
1/4 in sockets.
Suspicious smoke stain over 7809 is just chimeying
With LA2785, TMP87C846N
A1A4M oddly a digital transistor (GA1A4M like?) buffer perhaps used as a
semiconductor fuse in effect, 2SB116 . To p4 of TMP... via 510R
Bottom amp feeds phones via 2 x 1K// to relay 1401
Top amp to ry 1402
phones sw to p1 of CN1403
With no CD or plate under, tie the front of the chassis to the rear , to hold together.
Join 2 rear boards and hold with 1 sc to rear chassis, leaving just the 2 CD ribbons loose.
11.7V on phones bypass and 0V with phones jack in.
Taking e-line base to 7.2V via test 330R from 11.7V , no relay click over.
All tr pins at 11.7V
relays measure 265R
Feeding 50mV 400Hz at CN1101 prved top amp ok , disconnected CTL feed from TMP...
Requires r/c to bring up rear amp vol ?
C1237HA p6 is floating around oV and will go to 11.7V if droppered voltage diverted downstream
Representative good from another make of amp and active good
0,0,0,1.7,0,.8,2.2,3.4V
this one
0,0,0,tens of mV, 0.2,3.6V
TMP87CP64F p13 low, presumably goes high on some fault state , then via Q812 ,
disconnected to check
Replaced 10V ,100uF, still .2V on p7
replaced the SIL
901 , 30 percent mains
8.3, 5.4, 2.7 p8
60 percent 18.2,10.8,3.4
12K instead of 34K dropper
1.7V at p7 with 3.4V at p8
4.7K at 100 percent mains and 1.4V at p7
Worked but poor power-up , isufficient current or loss of hold-off / hysteresis
so relays buzz before turning on proper
Reassembly. Fix metal plate part, front to rear, 2 small sc plastic to plastic
at the front. Fix speaker output board in place and then
rear horizontal board.
Refit CD deck ribbons and slide deck onto the plate , introduce the CD drawer from the front
and replace top clamp section and screw in place.
The machine sc are for the tape metalwork
Sony TA X22, 1983
Heavy smoker gummed up the volume tracks with tar.
To remove the front panel remove the front pcb
screws and 2 lamp panel screws. Then 2 screws above
the slider pot, gives enough space to desolder with all
else in situ.
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
Teac CR H100
a junker but some info may be useful
To remove the CC display pcb lever off the coder/vol knob and undo bush nut
uses KSS213C optical unit
uses STK4132(II)
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 C2000
Control amp / preamp , 1992 on the motor
Long rivets to grind off and star circlip,
best ground off. Unusually ,
constant but fairly low level of crackle over 80 percent of one track.
With this sort of problem cannot see resistance amisss by checking with a
DVM.
Worn track but only worn down, not through. 3 sets of wipers per pot and 3
circular paths, conductor, 100 K resistor and low resistance inner ring of
about 20 ohms around.
Probably problem due to corrossion over most of the wiper fingers and this
central contact ring.
The pitfall is a not noticed/seen, presumably cartouche shape widget, that
locates that shape hole in the pot paxolin to the smaller same shape of axis
shaft. I must have removed both together thinking they were one part and
lost the widget before placing in tray or sticking to something else and
losing. Had to fashion one from a couple of transistor insulated washers and
epoxy. Nylon washer squashed and then fitted over the sahaft and fitted
in the paxolin, 4 bits of toothpick to centralise and a few preliminary
spots of epoxy. Making sure that the zero volume position was 0 ohms
on the tracks , 0 at top of scale does not matter.
Then full epoxying in.
Replaced the circlip with a small grubscrew boss as used in
clockmaking, leaving room to engage with the recess in the motor
sub-housing, in case the slip clutch needed adjustment.
Wired through as 2 loops instead of the rivets.
Remember to replace both securing/grounding plates
on reassembling the sections of the pots.
The SU C1000 has a battery back for this, but no battery pack in the C2000
unless it is somehow hidden in the faux (poids for your bucks) heavy metal
sub frame. No monster caps either , so what is this all about ?
From the C1000 repair and user manual you press a button to opt for battery
operation for no mains hum/ fridge spikes etc presumably (if/after the
battery is charged off
the mains) or opt for mains power to the preamp. So I assumed the same with
the C2000 but no battery or battery switch or anywhere obvious a missing
battery could be/have been connected/located.
Looks like a regular linear ps to me except for the transformer being about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.
There are 2SD2037 and 2SB1357 ,probably as pass transistors downstream of
the 18V regulators, using some of the headroom to drop to +/- slightly lower
rails and a load of little electros, which doesn't strike me as particularly
groundbreaking, let alone simulating a battery.
Technics SU V3
Bad input selector and vol pot
amp full of dust and nicotine.
Blew out. Reconned vol pot
Unclipped selector ribbon from sw housing.
Used foaming oven cleaner inside the sw mechanism activating slide every
now and then for 30 minutes
With amp tipped slightly brushed in meths to wash through and into tray under
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 V303, poor function switching.
Uses slideway ribbon interconnect between front
panel and pcb switch 6 way 4 pole.
4 long sliders, 3pin gap 7 gap 4 , and internal
long bars covering the gaps giving awkward to trace , 2 pins
folded under prior to soldering. Small ICs have this away from corners pair of pins
folded under also. Bend back each
corner of the desoldered switch to release the
base. Hardened grease, nicotine and corrosion.
To release bottom panel of amp one edge
needs
prizing off. As does the front panel after
removing knobs, 2 xLED pcb.
To replace one of the speaker plastic knobs,
pull back the non copper conductor that
is just pushed in to make contact to
allow turning of breakable captive end lumps. Broken ones replaced with wire stubs
soldered in place and fed through 20mm collet knob covers , pierced, to
cosmetically disguise, then choc-block.
I last saw this amp 2 years ago,
loss of some function switch function.
Same problem this time. Then it was a build up of black copper sulphide/
silver sulhphide? forming a black insulated layer , eventually too tough for
the sliding phosphor bronze contacts to break through. The structure of the
switch with 1mm gaps between the static contacts means it needs lubricant to
overcome the sliding contacts slipping in and out of these gaps or I imagine
they are likely to buckle and jam. Sliding contacts seem fine, they retract
fully on removing from the static pins, no distortion. No trace of
corrossion this time, good to see that worked, but the lubricant I used
probably did the same as the original sulphide and blocked contact ,
thickening over time perhaps. Previously I cleaned out all the corrossion
and ex-lubricant goo and then used a mixture of silicone paste and graphite,
only signal levels, so not too concerned about stray graphite conductive
paths, >100Kohm or so.
I was thinking this time to totally clean out , rotate contacts 180 degrees
and use a liberal amount of graphite only in the recesses as a dry
lubricant. Then when switch is resoldered into place surrounding the whole
switch with a membrane to keep the graphite inside. Or much the same as
before (5 years is not too bad any way) but less silicone grease in the mix
proportion. Too little grease and it will not stick to the contacts. A
different sort of grease perhaps with the graphite .
The conflicts are
Keep corrossion at bay
lubricate sliding contacts
retain electrical conductivity in static posistions
sliding contact pressures cannot be increased or they would score into the
silver plating or jam and then buckle
long term material stability
You could do away with
lubricant if you filled in the gaps but then there would be no cleaning of
the sliding contacts on each slide movement.
Normally the gaps between the dual-in-line pins 2x13 here would only have
0.2mm or so spacing to maintain electrical isolation and unobstruced slide
action but these ones have large gaps and consequently have more requirement
of lubrication I would have thought.
The stop/go resistance to movement is much more than normal "wave-band
change" multiway multipole slide switches
Decided to redo with molybdenum grease as more oil by nature to start with , adding
graphite it becomes a paste. It would be possible to solder runs of turned pin socket
to the switch pins and solder more lines of sockets to the pcb to make a breakable joint.
Molybdenum grease certainly migrates well for anti-corrossion purposes. I don't know about
compatibility, no incompatibility observed between silicone, graphite, silver, copper and
phosphor bronze.
But decided to resolder .
Another time crackle on one channel all inputs, phones ok
Cruddy speaker contacts, the fixed contact inside a terminal is a sprung piece of copper
pushed in to make touching contact with the plated brass riser from the pcb.
The 2 short red screws are for the underside panel, front anchors
Technics SU-VZ220
The sub circuit board with the volume control was
not seated correctly to the socket on the face plate
assembly circuit board
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.
Technics SU Z45, amp , 1982?
one amp shorted due to beiong dropped or something
Too many cracks in the phenolic pcb to repair reliably
with the large hole fo rthe heatsink, weakening it
Uses C3181 / A1264
C1913/ A913, 330R, 2x 560R, 4x .22R
From the working channel o/p Tr 0.6,48,0/ -.6,-48,0
no load and 1.2,48,0.6 on one of the TO220, forgot to measure the other
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 AX396 , 1995 or 2005 ?
Chip datecode year of 5 , not 1985 as DVD input, service manual for the AX496 refers
to lead in the solder but not RoHS or WEEE so probably 1995
Grease problem in input select rotary encoder , inputs jump all over the place on turning
and cross over of audio feeds.
Removed and cleaned out all the grease. Easier said than done
Remove knobs and front cover. Leave 2 screws in place unde rthe "letter box" cover, remove
sub front screws including the one inside hidden under speaker A sw.
Undo bush nuts , 2x m/c sc of CD/DVD sw. Snap rivets with heads on inside surfaces.
sc behind tape mon
rotary encoder contacts are between the dedents
Forgot to check for cross-over problem but as amp did not return I assume that went away
with the encoder clearout
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.
Yamaha GE20 graphic equaliser
Dropped or front stove in so mechanical damage to pots etc
R101 5.6K, uss B647C and D667C in ps
CD players
Ariston CDX 720 CD, 2002
Uses Sanyo SF P101N 15 pin optical block. No dull red glow and no response from IR
photodiode to LED test , 4.6V at the laser pin. Chuck it job presumably, no
point in exploring deeper into the optic block
Traverses and focus hunting.
4.6V supply to laser pin
.6V and 1.3V diode test either side of mid pin
with ribbon disconnected
Nothing on the box of the new one about the shorting link, only graphic
showing use antistatic wrist strap for assembly
Do they all have these solder-across semicircle land pairs?
This one Sanyo SF-P101 has them , so do KSS213 and K SM213, all ?
Is there something in the laser assembly that is especially prone to static
damage, considering the antistatic assembly was inside a static bag inside the box?
Uses Samsung SiL9223B01-go - KB9224 , note 22K mentioned on the useage cct at the
pick up maybe 22R, as 100pF and 100Uf caps and transistor otherwise agreed with this
use. Transistor TO92 B546A probably.
Antistatic link across the laser diode, 1.3V diode DVM test
CN15 line 5 to lens side pin of 3 pin laser unit
6 to centre, 7 to 3 rd pin and line6-7 measured .63V on DVM diode test.
Powered up measured wrt large h/s (phonos ground not connected to chassis)
to line 4,6,7 in play is 1.83V, ,01V,.162V with preset set to 1280R
Cold diode/R testing of new good laser
.63V,1.36V and 2.6M,10,4M
old bad laser no different really
.61V,1.37V, and 2.4M,12.4M
powering from 5.1V via 22R then 4.8V over laser, similar to 4.6V when as original in chassis
Track 1 of 10 in play and DC at CN3
3.4,4.1,2.5,0,3.8,3.6
trachk 10 DC 3.6,4,2.5,0,3.8,3.6
CN312 3.8,3..8,0,0,5
DC at R7, 22R, 4.2V and 5V
5V line at J35
Also uses Fairchild KA9259D
CD in play then drawer sw at 5w ribbon R/Or wire is 0R but when at out position
then R/Bn read 100R to .5M
Ribbons disconnected motors measured 2x 10.5R and 8.5R
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.
Followup - well not so much the connectors but manufacturers that use them , supposedly
fixed to too thick screened cable, this time Van Damme.
The bifurcated "cable clamp" does not grip the sleeving, so free to move and
then break the signal line at the phono.
Adapted the smallest of Jubilee/ metal hose clips so it could pull round
even smaller than designed. The rack that engages with the pinion does not
continue right up to the anchor point.
Bend back the spurs that retain the pinion so the pinion can be removed
after releasing the free end of the track. Cut that anchored end off the
track and reform the joggles that abut the anchor/housing. Make sure it will
tighten to something like a tight circle, 6mm here, of course the anchor housing is
flat.
Also make sure the free end of the track will easily engage and disengage as
once the job is done you have to release it.
With connector shroud on , introduce the connector clamp to the sleeve
(leave soldering the conductors to last). Tighten the Jubilee around, over
as small a part of the connector clamp as you can, on the up cable side.
Turn some turns of tinned copper wire around the exposed cable clamp
sections , twist the ends together and solder into a ring, beware of melting
the sleeving, so do in stages.
Remove the Jubilee and maybe grind off any excess high spots of solder.
Remember when soldering the rest , the screening copper is soldered tight
and the conductors cut long, to allow for some relative movement inside the
cable , and so, in service, not straining the solder connection. And, normal
good practise, mate the plug with any old socket before soldering the
conductor pins.
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.
Denon RCD M35DAB, CD of 2006, so far so good
reads Tr 00:00 in display only
Cut into the top clamp support to check for laser light/ photodiode test but no light
Neither me or owner will spend out on a new optical unit (failed laser), big spondulics. But a near industry standard KSS 213C looked somewhat similar , so I tried it out. This one laying around , unknown condition, from some scrapped something. The ribbon feed lines for the 3 laser pins matched , the other 2 deck motor+switch leads matched up, so tried it out. Laser lit but logic of the end stops wrong so swapped the optical unit across to the original (scrapper would not have mechanically fitted in the Denon anyway). Required some bodging to fit, straightforward but too much for detailing here, but sledge etc worked .
Adjusted power pot and cleaned lens and now consistently reads data track and plays about first 2 minutes track1 of any CD I try, faulters and stops, will not play any track 2 or higher.
LD line 10 of 16w ribbonvia Tr401 to p7 of TA2157FNG IC403
ribbon pins 12,11,9 to laser
With drawer open remove 2 sc + 2sc thru holes in drawer.
2 front catches need flipping , 1 upwards and 1 sidfeways to remove tray
I suspect the registration of the centre limit switch is out, but could be a problem with the rack although powers up and down the slide without incident with only 2 volt on the motor, but I will try marking rack and cog of the 2minute stoppages. I assume a new (cheap) KSS 213 would show the same stoppage.
Says closed when tray open , cable from both decks joined by 5 pieces of single wire to reverse the pimming.
Unclip the magnet to remove top clamp to accept sliding of the rod
So how to adjust the end stop , ? pieces of shim material added and subtracted in the gap between sledge and leaf switch and suck it and see? or some other problem likely?
I changed the position of the central limit switch action point by 1.2mm and the same play for 2 mins only.
The Denon optical unit , marked Sanyo, does not use the usual double-rack anti-backlash arrangement but a much cruder sort of sprung plastic arm tensioner via the mount of the final double cog. I had to remove the second rack on the KSS213 to fit in the available space.
Break of fthe 3 holding spigots, too easily done, extend slot in deck to allow spindle of final cog to lift a bit as it
fouls on top of the rack. Maybe relieve part of black retaining cover as may foul that.
Check movement with 2v on the slide motor.
Top cover needs 3 cocktail stick tips cut off and wedged in , then hot melt to make sure the
nibs do not unclip and jam the tray movement
To replace tray align crossslide cam-way slot on the tray
The tension is now too high, the rack must be .5mm or so wider, and I'll have to find a way of backing off the tension. The final cog to the rack is 12 teeth and I can feel resistance 12 times a rev. Running the motor continuously , even at low V,the inertia overcomes that lumpiness, but that is not representative of the normal radial stepping drive, as you say.
What a pillock, the racks are 2 different pitches , the KSS213C one something like 21 teeth per 20mm and the Denon one is a bit coarser, I assumed that all such racks were the same. Whether the final cog will swap over,and tooth pitch mismatch betwwen cog and cograther than cog and rack, will find out later
The Denon optical unit is labelled CD11FTA3N , unless you are aware of its Sanyo number , they are expensive to replace, presumably specials produced by Sanyo and consequential markup.
I melded together a 1.25mm pitch cog with a 0.95mm one with only about .2mm ecentricity but much the same result. Back to back cogs in a clamp, existing mould line as a guide sort of chain drilled
0.3mm holes throuigh both flanges, next time use .5mm as drill bit flexes. Start drill slowly
then speed up. Fully cut the drill hole line and tidy up . Try one in the other and spin on a drill bit to
check / shift for minimum eccentricity, super glue togrther.
PTFE guide pin fixed to the other side from the rod, of the optical section
Optical coils pinning from one end of ribbon
1&4 , 1 negative, focus outwards movement
2&3, 2 neg, tracking moving inwards
Top clamp magnet , dimple is uppermost
I've now noticed why pre-selecting track 2 or 5 or whatever results in no play. The sledge is propelled to the periphery as though track 10 was selected, so something wrong in the interpretation of "0" track data ? or something beyond any resolution by me unless anyone has any insight?
The cheapest I found in the UK was , with all the usual extras about 90 pounds. Much more interesting playing around/hacking. No guarantee that there is not some sort of random ps or other surge that knocked out the original laser and could equally do the same with a 90 quid replacement
The number on the Denon Sanyo one is SF-P101N but as that is on the plastic of the body rather than a label, there may be a lot of flavours.
The optical unit just carries the laser , the receive photodiode matrix , and the focus+track coils. Could the track coil polarity be wrong?
2 minutes in could be where the sledge has to definitely have moved as come to the limit of the coil shift ambit, worth a try . Now what differentiates the orthogonal coils? A small voltage in each to see if the lens moves vertically or radially I suppose. Nothing like heuristics, its not as though the owner is paying for my farting about.
Same 2V polarity on lines 1 and 4 of the ribbon send the focus the same way and same for lines 2 and 3 for the track throw for both optical blocks, so nowhere left to go
The SM (listed RCD M33DAB) has the test mode details. May as well try it as does not seem to require a test CD. although at no stage has it registered one of the 20 listed error codes
In the meantime
It all seems mighty weird that you can progress flawlessly through the test routines along with never any error statements but the unit does not work.
Test routines pass byte info out on focus balance, focus gain,track balance , track gain , focus offset , track offset,RFRP and a routine that sums errors in a 2 second sample. Go into the auto adjust routine after adjusting the power pot and the values change. I don't know what 100% error figures for 2 seconds would be ,but readings about 023,000 one time then adjust pot and then average about 035,000. So if 6 digits is 100% then about 2 to 4 percent. What would a representative figure be for dust,microscratches,scatter etc ?
Not easy to desolde rthe laser solder short , so remove before placement, with ESD precautions,
adjusted level pot to near 1077 ohms of the original finding
Sanyo one in there and working all functions. So bulk standard cheapo with no added Denon flavour it would seem.
BER error now about 100
Quite happy with BER of <>100 but I assume this error reading would be a good monitor , not immediate though, for adjusting the power pot for optimal.
Other test readings
FB FD
FG 00
TB 05
F8
01
00
00
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.
JVC MXD 752 CD etc compact audio unit, 1998
Had a history of sometimes a CD stuck inside but immediate problem was
a broken end of 3.5mm jack inside the socket stopping speaker operation
white + grey connector . pull the white outwards to release .
Remove 2 front and 2 rear screws to release CD unit.
Slacken top 3 rear panel screws to give some leeway.
Undo screw at phones socket to release that small board.
Jalco black and white socket.
1,4,2 pins in order
4 are 2 sw , open with inserted plug, via relay to operate dpeakers
2 pins are tip and sleeve lines.
Lever the white rear protrusion at the pcb and this rear section will pivot
and unclip 2 top clips, holding the insulator inserts for the sw action.
Bad solder on rear speaker connections.
Unclip bottom interboard to release the pcb. To reassemble that pcb align
innermost end of interboard socket , then push down and out to pass the
sp conn through the chassis
Uses "3 disc triple play , play & exchange" 3 drawers stacked over one
another and the CD deck on an elevator system to access them.
Uses 4 motors in all. The elevator
cylindrical cam actuators and a mode switch, 5 +5 traces to the
10 way to interboard connector.
The XC10 has much the same info (or not), exploded views only. Desoldering
the 4 CD deck motor points and removing the main pcb along and knowing now
being able to power ordinary motors, outside the chassis, should ellicit
enough.
Using 8V one motor powers the shift helical cam and the other moves drawer
and sub draws in and out and the CD deck up and down via a PTO linkage and
its helical cam. Limit switches work as well. Leaves just something wrong
with the mode sw or "cam switches" as JVC calls them. There is the matrix
for all those in the manual but to progress all that manually seems too
much.
the CD changer mechanics look the same as the older PC-XC10 , the active
electronics board is different.
5 wire mode switch inside each cam and separate 10 line connection for limit
switches. Cams driven by cog train from a standard DC motor each ,
elsewhere, so 4 motors only. One for trays and one for CD deck elevator.
Will try some DC on these motors and see what happens.
Front most motor for tray select helical cam., Other motor is deck elevator
so 2x 3 positions. When pivot arm on lower section of this cam is free to ride
upwards (in area of slot) will then engage tray in and out powering.
To manually pull any tray forwards pull the 1 of 3 white protrusions on the left hand
side to unlock. Trays consist of 2 parts the minor section slides the CD from half way
and into play posistion.
Tray limit sw closed in outmost position and one of each closed in the mid 2-tray
transfer posistion, swapping the drive cogs on the left hand side vertical array of cogs.
To remove upper pair of trays, to view interior in operation, flat blade under
the curved end stop tang and lift the side lock manually.
One screw holds the top clamp section in place, remoive and replace with
a free magnetic disc to try out.
No problems found so decided to cut a rectangular hole in the thin steel outer casing,
protect with grommet strip and show the owner how to unlock the tray with
the 1 of 3 white lever sections on the side.
Dirty lens stopped the spindle motor to even kick.
Top 2 pairs of limit sw need taping down to
function with top trays removed.
To unclip the front of tray cosmetic labelled fascia unclip ends upward
and slightly bow the centre to clear the small locator stubs.
If the deck is up , in play position, the inner subtray will be locked in place
by a black pillar and releasing the white lock on the side will not free the tray.
Wire link at top , single joggle goes in slot of CD top clamp,
double joggle to top cover.
To use the side access delatch pull out top tray
first if possible then half way in can get finger through hole in tray to pull
out middle tray when manually delatched at the side panel hole.
Alps green vol control , rotary encoder, almost impossible to control
volume setting, removed and cleared out the grease.
Service manual for MX D451 is similar
With RH cassette stuck in deck and clanking move the grey spool to engage PTO
to release the front flap
To get to encoder remove large board , then sc and dislodge small board
No tape functions bands measured 250 x 1mm unstretched, stretched to 278 measured
around path so 11 percent elongation and for tendssion stretching from 250 to 320
was 330 gm when doubled up
To get to bands undo 2 x tape head ribbons and reinforce before refitting.
Unplug 2 headers . Remove 6 sc to remove motor plate . Mark posistions of bands
as not the same. LH deck is topmost of paired drive pulleys.
Broken boss to the double drive pulley. 3 wire turns and twists on the free pulley, 120 degree
apart and then hotmelt glued over. Boss nearest motor. To reassemble
motor plate. Place both bands in place on drive pulleys and turn and tie off on the
upper face of the plate. Keeping some tension in each band tie off with bands in place
simply around the pulleys. Then place the band in correct path and check for band twists.
Check by hand all pulleys turn as one in correct senses.
At CN309 p9 of 10 way ribbon should be 8V for motor drive.
To check motor running apply about 4V to the pcb electro that is over the motor supply.
Noisy running , lubricate the simple outlier black pulleys . If you pull off the white jockey wheel
assembley then the plastic circlip will fall off and you will have to take
deck completely apart to refix, the 8 screws , comes away cleanly with no awkward
springs or linkages . This is tapered plastic "bearing" and spring
must be there to make sure it does not "wedge" in. If no take up spool drive and then
perhaps this white cog part is out , due to the spring and no circlip
at the other end holding it in.
If cassette in place but "no tape" in display check the 11 way ribbon is inserted correctly.
If problem replaying CD or enigmatic TAPE 90 in display at power up. Press
program sw , probably in program mode . User manual not seen but apparently
in the service manual for the MX D551 for perhaps similar
With just one ribbon from ps all lights on but no tape functions
That and ribbon from tuner to CN305 deck FWD and REV , SYOP and EJ but not play.
Can give a bit of working space of 2 inches by screwing and bolting a
pair of metal platesbetween base and front panel with tops tied together with cable ties.
JVC XL SV22 video CD player, Karaoki, 2002
Chassis stmp date "7 Aug 2 "
Intermittant 1 ch , due to streesed solder , only 1 fixing screw
Jumper wired back to a pcb point and resoldered
Panasonic RX DT401
Select CD and just the slight clicking of the focus mechanism.
With lid up and paper folded into the usw slot will recognise "no disc"
and dull red glow of laser, seen off-centre.
10 sc to separate front and rear halves. 1sc under vol knob
plus obvious ones to remove top cover
Optical deck RAE0111Z, E111 embossed in plastic of the deck.
Platter slid down the motor spindle, so CD touching deck probablty as no spinning disc
after trying when encased. And CD lens touching , scratching CDs and scratching the lens.
Small sc driver in gap at open end and fingernail on opposite side to
move platter back to some playable posistion, if the lens was ok. Would eventually
glue with hot melt dot , not superglue.
Checked traverse motor and belt was functioning , removed 3 pcb sc and desoldered
spindle and traverse motor pins. Belt ok and manually moved the spindle to leave
traverse in mid path to check moved to centre and back for TOC rread at sw on, yes it did.
To do this without desoldering the pcb a matter of melting a hole in the deck
plastic at the other end of the motor from the terminals, can just see a .5mm of the pinion
through gap in deck housing.
If resoldered minus the springs, these can be retrofitted, the one with a spine through the middle,
remove the grommet and then introduce spring one at a time.
With a needle lifting the lens carrier it will rise
to the level of the underlying deck, combined with some inertia in such a
flimsey mechanism, I could quite see the lens hitting a CD that is
erroneously spinning only just above that level.
The scratches are otherwise in a neat circle around the central area of the
lens only , so unlikely done by a hand.
Duraglit sounds a bit drastic , doesn't it have jeweller's rouge or some
abrasive in it? but as useless as it stands then nothing to loose , now to
see if I can dislodge the lens without destroying the suspension frame
I can pull this lens suspension up and it stops with top of dome perhaps
.5mm above the underlying deck area and has no protection ring, add in some
inertia to the kicks and and I'm pretty sure it would be hitting any CD once
the platter had dropped on the motor spindle. I will try jigging/temporary
anchoring the lens into that position to work on, as to get to it otherwise
looks as though you have to take the whole laser assembly apart or at least
a number of set screws that are adjustments of some sort by the look of
them.
3 brassy sc to remove pcb , desolder traverse motor, pull off the platter, 2 sc under.
sc retaining slide rod and remove through hole in the other end
undo 2 sc at the traverse motor only , not the third at the end of the helical drive rod.
Motor , cogs and band comes away neatly as one piece.
Black cover and 4 nibs prizes off eventually.
Managed to break a wire for the coils and whatever I did , I could not remove the
lens to try a swap , so abandoned it.
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 CDR775, 2000
dead
bridge rect , fuse 22R and 2x 18K ok
UC3842
Driver P3NB60FP 600V 2.2A
1 gnd, 2 +12, G, +5, -8V
23V on 2x 18K supply
2 wire line just a shorting line
hot h/s low side
cold h/s gnd
>300V retained on mains cap
replaced UC3842A with UC3842N
low voltage side D6210 , 0208GSB360 s/c = SB360 60V , 3A shottky Barrier rect
Replaced with MR856 high speed , not shottky, diode, still no function so returned original UC
and working order so some difference in the UC operation ?
Comes up after 2 second delay , 8.2R 5V load
-32V and p1 to p3 floating 5.6V dc for CC display
REC disc plays CD but play deck accepted and spins
but says no disc, insert disc
Left deck
4 chassis machine sc, turn over , 4 pcb ms, then gently move pcb to side
and 4 pk. Slide both sections out of frame , careful of film ribbons
Unclip top clamp (one clip broke) to reveal laser and lens.
Hold deck above pcb while powering up , laser lit, sledge ok , platter spin and focu servo ok.
External ribbons wide one is ZIF, internal foil
ribbons both ZIF. Undo 4w power conn then the foil ribbon , leave one power 4w connected.
PCB foil ribbon connectors are inverted wrt the other. To refit short ribbon , 1mm
card next to the socke tto guide ribbon in.
2V on sledge motor to propel out to check rack (worm drive so no manual movement)
Adjusted power pot , monitor value on central
wiper and w3 of the ribbon was 275R, adjusted to 215R
worked, so adjusted up to 245R and reassembled
Philips VAM1250 drive number
Top clip , pull back clips before pushing
home , not by simply pushing , angling th eframe.
with 4.1R W/W as 5V load and no connection to the 2 pin conn
Philips FW-R7/22 , year 2000
Intermittant loss of a ch
2xBD438, 2.5A fuse one end of h/s
2x AN7591, P16NE06, BDX53, BDW94C, BD438, 2x 3.15 A fuse
Note sc types on removing, especially the rear cover .
PITA mains cable clamp. To replace, remove the plastic widget that
drops away with undoing the external sc, open out the hole to accept a longer screw. Requires
joggling into place, pulling up the sc head when located and then tightening.
Broken solder at the sp outlets, redo and double up with 4 wires between the actual sp
terminals and solder points on the pcb
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)
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 .
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.
Sanyo CDP 350 , 1995
Gaffer tape gum getting into the jack connectors requiring
getting inside to properly clear out with meth wash etc
Open lid and small blade in the hole near the battery box to
release final hold point. Desolder earth pointand one screw.
Leave slide sw cover inplace.
Remove laser data ribbon from underneath rather than at the laser unit,
pull closures.
Sharp XL521E, 1998
not reading TOC/play of some discs
Power pot measured 376R. 303R functioned ok , as did 351R , settled on 313R
.4,7,13V pin 2 voltage
Sharp XL 521, 1997
no disc play
remove sides and top CD deck
remove flap sw pcb and tape down the sw and check for laser light
If "cd" shows no "DISC" word then check this sw
advanced pot from 320R to 300R
if advanced a few tracks would sometimes start 10 or 20 sec into the track
Adjusted down to 264R
Sharp XL 251
as above, 283R down to 218R and then back to about 230R as optimum but would
still sometimes start after the beginning of a track if advanced , straight through read of a disc is ok
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 D-NF007, plays fine but growling noise
Worn motor bearing, remove platter with 2x plectrums and a blade.
Platter surface that touches a CD about 1mm above the deck.
End of motot spindle .2mm proud of the boss
obvious sc + 2 catches under battery flap , desolder 4 wires and carefully pull out the
ribbon, wrap before reinserting
Remove motor
grind small flats on each side of bearing, then //jaw pliers . Lift using the 2 "wedge"
faces of small end snipo pliers to pull off. Mount in Jacobs drill chuck and tighten to finger and
count fractions of turn more and tryover spindle.
Bit too tight, left motor running on a ps until bedded in again and motor would
start with 3V
Plasticine in the flap switch hole to try out. Sometimes would not start , not
bedded in enough , 5 attempts to spin then stop.
Simple had flick of the unit , when trying , in an anticlockwise sense
would inertially start the motor , until bearing bedded in again fully
Sony HCD NE3, 2004, Pbf
KSS 213E
"No Disc" - how I hate lying computers, "no data" - fair enough.
Top flap remove damper and pull flap into the encloure space
while prizing back the spigot.
Dull red laser spot, focus and sledge operate correctly, spins up, until
stopping after third attempt. Cleaned lens, and internal cover glass. Good
cap ESR, both ribons check continuity ok.
Tried adjusting power pot a bit but no change.
Pushing the sledge cog around either way , the servo will return it, so
focus presumably ok.
Sometimes it will sit with "reading" in the display permanently and disc
spinning almost top speed until switched off. Where to go next? I've another
(salvaged) KSS 213E, unkown condition , will try replacing but I suspect
something more downstream.
I did not expect that, slid out slideway rod and swapped KSS 213 and the
thing worked without hickups. I assume that there was enough operation to
set the focus coils and sled to zero-in on track 0 but not enough for data
readout.
It was PbF solder for this one although 2004, could be something to do with
it
Unclip final cover over laser unit at sharp end of metal plate, undo 2 screws
to release the focus unit.
6.4 and 6.4R of coils across pads near the lens, 7.1R ,7.1R at connector
Bad laser unit .74 and 1.31V DVM diode test
good laser .56,1,43V
Sensor array with DVM red to 'C" pad. Diode test
1/63,1.63,nc,1.58,.91
.89,.72,C, 1.5, .86
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
Pictures of the
mechanics as they do not seem to be on the www
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.
Ekco CR280 , 1950s
to check-over/repair as no known history and not powered up in any way
http://www.diversed.fsnet.co.uk/cr280.jpg
Took apart section by section with bits in separate labelled bags
I will test the valves later today
Seems surprisingly good condition inside. Will have to replace the 12V (-ve
supply) lead and speaker lead as perished and the on/off switch is ohmic.
The vibrator had obviously been removed at some point (putty-stuff is split)
in the past.
the output matcher primary 692 ohm and secondary between 0.1 and 0.2 ohm
had to replace a number of corroded/failed socket contacts
and now have all 4 heaters working . Valves all tested ok on Avo CT160.
Vibrator is working giving HT1 of 130V or so on low volume and 160V or so on
high volume, yes that way round, should be about 270V.
heaters of valves 1 and 3 connected in series, as are 2 and 4
ECH42, EF41, EBC41,EL42
DC readings for mains derived HT1 of 160 Volt on umbilical wrt casing (+ ground 12v)
-5.7,130, 66,-7.6,34,-.6,0,0
-5.9,130,0,0,34,-.58,0,0
-12,55,-.7,0,-.36,-.36,0,-5.8
-12,144,13.4,nc,130,14.3,13.5,-5.9
heater Ra 4,5.1,4.2,4.8R
Severe noise crackle on speaker that varies across the tuning but no hint of
radio reception. Next stage is to separate ps and radio sections by making
an umbilical so I can monitor the valve base tags, but where to go next ?
Overall consumption should be about 2.7 amps at 12V
Unfortunately both bell-mechanism and rectifier would seem to be in the
vibrator module, and transformer is external, shown in lowest view of the
pic.
I first tried to find some info on the vibrator to confirm it does have some
sort of rectifier inside.
The vibrator has some large slightly loose lump in there and a small loose
something if turned end over end it rattles to the other end, but I won't
try going inside.
I warmed up the mastic/putty on the vibrator enough to scrape off with
mark-one scrapers to reveal.
Wright & Weaire , London
Synchronous (self rectifying) Type QFA/12 12 volts vibrator
http://www.ferrograph.info/pages/ferro-history.htm
Wright & Weaire Ltd.
Rectifier-less circuit magic presumably by this circuit
http://www.diversed.fsnet.co.uk/vib2.gif
feeding back output pulses
from a Quarrington book , 7 pin minimum agress with what I have here, 7
pins, and wiring back to the transformer agrees. So just coil of 28 ohms DC
and 2 pairs of contacts in the case. fed some decent, known good, DC
into the radio via a
ade up an umbilical and a mains variable raw HT1 supply.
So 12V dc from normal bench supply feeding heaters and with vibrator removed
some HT feeding DC to HT1.
Strange dealing with radios marked in metres, I expect the Home Service
rather than the Boomtown Rats coming through.
Needs alignment, as very good response 1900 to 1500 metres but poor down the
1000m end. Works, sort of, with HT1 of as little as 50V. Took valve base dc
readings on HT1 = 160V, as a bit of a lash-up.
Works perfectly ok at 260V ,on the end of band that is, but will try sorting
out the vibrator first before taking any full HT readings.
With a 100mA fuse protecting my HT transformer plus variac I have to start
low and build up or the fuse blows but otherwise current of 27mA at HT1 of
50V, 27mA at 160V and 44mA at 260V which is as expected
The mechanism of the HT vibrator is mostly covered with soot? but not the
sponge liner shown in the third image, how come ?
http://www.diversed.fsnet.co.uk/vib.jpg
Ground around the rim of the base to reduce metal thickness before
prizing back to release the black disc. Before returning to the can
pulled back the foam at the join and placed some activated
silica gel in there, closing the base, and sealing with hot-melt.
The small rattling piece is a contact that has come detached from position
to the left of the purple \ and shown in isolation as the black dot on the
second image.
The adjustable frame contact is just above the purple \, coil to the left.
The vibrating strip is central terminated with the iron bob next to the coil
pole piece.
Can opened easy enough and room inside for a pouch of activated silica gel
before closing and epoxy coat sealing.
a synchronous vibrator *can* be used with opposite ground by simply reversing the two transformer secondary leads that would
normally go to the plates of a tube rectifier.
Useful to know that polarity reversal point for a future occassion. This is
a positive earth only radio, no user switch, going back into (another +
ground) such old vehicle.
The contact is 4.4mm across and I have successfully robbed a contact from a
20 amp ,12V automobile, relay which is about the same size. Swaged
it (with a ball bearing and vice) into this mechanism after grinding out
the copper back pad of the original. The spot weld ? had failed between the
platinum? pad and copper back pad.
Found out why there was ohmic path on one of the contacts. Insulating
plastic sleeve around one of the bolts had burnt and charred, shows how hot
the contact arms got. Some of the high temp sleeving for 1/4 inch spade
connectors just about fitted there, original 8,8mm long, 4.6mm ext
diam, 3.3mm int diam. Had to replace the mating contact as
that had a great crater in it as well as the broken one. Had to remove one
standard rivet and replace for to be able to get to the covered contact, to
replace it.
Then reassembly is a pig as dozens of bits of mica etc .
I replaced the 4nF, 800V on the HV secondary with 4.5nF 4KV.
Testing the old one, it did not like 500V of a megger up it , it went short.
Radio is now working all on 12V , but not sweetly, as no can around the
vibrator and no casing around radio and no screen at the final EL42 output
valve. Sparking on any of the contacts is barely noticeable even in a
darkened room, I expected quite a show.
Adding 500 uF to the HT made no difference to the hash , so hopefully due to
lack of screens.
Vibrator on 12V , current unlimited,pulling 1.2 amp with dial bulb it produces HT of 300V cold ,dropping
to 210V in use. Upping from 12V to 13V then HT goes up to 250V or so in use.
ps transformer HT 493, 707 R , LT .7,.9R
Then adding FM using the board from a miniature key-fob FM receiver
using a TDA7088T. As the Ekco is positive ground , zener and
1000uF, 560R dropper supply for
the TDA was 0V and -3.3V. SPDT switch changing AM to FM
at the input to the volume control, adding 1M to the
AM source. Added 330 ohm in place of removed earpiece
socket and added per datasheet 68pF/82pF/70uH
at antenna input and repositioned the grounded 220pF. Added 20K ten turn pot
for varying tuning voltage to the 5K6 resistor
going to the varicap and took the muting pin high via 27R.
And cut the cap to the tuning "run" input.
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.
Japanese Transistor radios, pcb marking MEP 16 issue 6 , probably 1972
transistor CCS9018E105
As read around the barrel, one gap only between 5 and C
from someone's cherished 1960s Japanese radio. Only a signal one , probably
Si in otherwise mixed Si/Ge.
Form like 3 pin version of TO105 or TO107 , black dome, brown barrel,
slightly "D" plan view. Italic lower case f logo of ?Fairchild apparently
Another one of same brown and black domed form is
f CS13121 218
where f is that Fairchild f logo and a definite space between 21 and 21
I dug out an old ECA German data book and a
CS9018E equates to BF495, replaced with BF200
and CS1312I not CS13121 equates to BC307 replaced with BC309
it is just about possible, under magnification, to see horizontal blips top
and bottom of the "1" and a straight vertical line for the "I",
both much more likely in a small tranny
leaving the last 3 numbers , probably, date code for 1971 and 1972, or was
there Si in early 60s ?
For the archives , there are about 60 other CS.... types listed with
equivalents.
and Diode/ Transistor oddity marked CD0000
From German ECA databook listed as Ge equt to 1N34
This is continuing saga of 2 old Japanese radios that owner removed from
forgotten make & model cases and put in something else. One stopped working
a long time ago and the other just recently. I've repaired one so can
compare cold and active so no great problems.
Only marking on pcb is MEP 16 issue 6 , probably 1972 using Toshiba Ge
transistors and italic f, so probably Fairchild, Si transistors but
otherwise all else is Japanese.
This detector diode is o/c , is the black dome top / brown cylinder body
with Fairchild f logo and probable date code of 214. But it is obviously
made as a transistor with one leg crudely snipped off and .75V forward
voltage between the stump and one other pin. Obviously I will replace with a
Si signal diode but just curious , can anyone work out what is going on with
the labelling & Si/Ge business.
2SD96 replaced with AC127
Kenwood L-1000T , 1990
Expensive looking fm tuner not keeping stations etc in memory.
a workup to get to the stage of getting to the C11
supercap with only 1/4V on it. Anyone aware of anything else that needs
changing as a lot of normal electros on the Vdd line through different
parts of the kit. I will change the fractional farad (if I can find such a
squat one) but how to test these to confirm it is failed? charge to 5V and
time discharge through an R but what sort of value , high enough not to
phase it , and low enough for reasonable time to 2.5V? ESR I imagine is
irrelevant. Schematic is on e-service
Old 0.047F , 5.5V dropped from about 5V to 1V in about 1 sec with DVM load.
Replacement .2F one , connected to 5V ps via 220R took 35 sec to rise from
3V to 4V
Wiring across from the cavernous central space makes sense. The very squat
form factor of the original may well have precipitated its failure. I was
forgetting about all the diodes along the power rail route so only one
nearby standard electro (assuming the diodes are ok)
LA1247 AM receiver IC problem
An LA1245 is a pin for pin replacement but
slightly lower specs.
AGC line 2.2V low level signal, 2.6V high level signal
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,and remove screw under telescopic
and 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.
Poor connection to the telescopic, soldered a solder tag to the
bottom , avoiding solder in the tapped hole. Antenna cannot
then turn and loosen the signal connection,
Worn volume control . As awkward to remove needle point in the
gaps of both pots to adjust wipers to new posistions.
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.
Sobell 516 radio, 1947 to 1952, latest cap date 1946
Bought non-working years ago
Neat insulated deck suspension on 4 brass bracket
pins and grommets. Rear pair held with the back cover
screws and the front ones remain on the casing.
Worst of dust blown off with 1KW blower. Padded with
tissue paper around the base of the air vane cap
and washed out dust and fibres with meths on a long bristled brush.
High resolution scan of the dial taken as a precaution.
I thought the brown spots were rust spots but the backing is aluminium
One knob had a set screw broken so no one got inside years ago.
Instead of my usual left hand drilling out I tried masking under the knob
with glass matt and cardboard, heating the knob with low setting of hot air
gun for a minute or so , then removed masking and squirted freezer spray on
the pot shaft and the knob could be removed without too much force, not
possible beforehand.
Valves near enough as schematic test useable, inductive parts test out cold
ok, no ominous emanations inside and will try variac powering up , for the
first time in 30 years perhaps , going by the dust accumulation.
Nice looking front panel with sheened curvy wooden slats across.
As I knew this stuff was very good at removing nicotine staining.
It is over ten years old and no info on the aerosol can of ,
"Rapid Oven Cleaner" made by Robert Mcbride , Manchester, other than
irritant and you have to pre-heat the oven before intended use.
This is the before and after
http://home.graffiti.net/diverse:graffiti.net/sobell_dial2b.jpg
no brightness changes in graphics package, different scaling a bit.
As original, is the leftmost section of dirt on the lower image,
to the right of it where I'd tried plain water away from the lettering
and it just smeared around.
Squirted the foam into a jar lid and lightly damped a cotton bud and
lightly moved across the lettering in one go and one direction , sometimes
repeated but no more than that or it would lift. Firmer application
immediately around the lettering with blunted cocktail stick, then outside
that cotton bud and then outer areas cotton ball. Rubbing off the muck
around the lettering with more blunted cocktail sticks/ cotton buds. Dusted
with talcum powder , left overnight and then cotton wooled over to remove
the talc. Surprisingly good result, presumably the active
ingredient is sodium hydroxide.
changed mains cable and created
a cable anchor point as there did not seem to be an original fixing point
and added an inline 500mA T fuse, set selector for 250V.
Burnt and now conductive paxolin on a wafer switch
Anode voltage across this section and arcing to the grounded spindle.
I was only monitoring HT1 while slowly powering up via variac. About 90
percent mains and HT1 was about 220V , the HT on the wafer has 1.2K. 0.5W to
HT1. Not repeated as I've not ground back the paxolin yet, so reduce rail
loading, while getting some ideas. I don't know what HT1 should actually be,
HT1 rail caps are 350V rating.
It would just about be possible, in situ, to grind away the burnt , back to
good material, but what to do after that. Not particularly structural burnt
sectuio. With low voltage burnt polyester pcb then make good burning, from
overheating component, with epoxy after clearing away charred material. But
what to do with HT around ? 4 large wafers which would be a work-up to
remove one or all and then probably not be able to find a replacement
wafer/s
Removed the wafer , quite easily. None of the nuts & bolts here or anywhere
else show any rust but the whole radio was covered in cigarette tar staining.
What would have been the original cause of arcing ? Before taking the pic
I'd blown away a lot of the dust. The staining on the metalwork I would say
was nicotine in the main, not corrossion. Can heavy tar contamination
lead to a conductive path, perhaps in conjunction with hair/fibre? or does
nicotine take in airborne moisture ?
http://home.graffiti.net/diverse:graffiti.net/wafer1.jpg
(mm scale)
To the right of the arrow , I scratched (V shape) the surface of the
blacking and its not very deep. Worst area is under the arrow between the
spindle hole and the small tang below it, from the conductor ring from the
underside carying the HT. What I saw, viewing skewed as fibrous, is a
slightly different colour of paxolin as the 2 conductor rings are mounted
either side of a small paxolin disc , perimeter under the "R".
Cartouche shape in centre is where the spindle goes through, structurally
sound even most of where the arcing has been. One of the tangs from the
other side lies under the ring. These tangs from the front and back ring
sections lock this rotating disc together. I intend to twist back the tangs
to take the disc apart to deal with or would others recommend drilling out
some solder tag rivets to get to the paxolin disc ?
What looks like a worn hole on the edge of the spindle hole, under the "R"
,is at manufacture, probably an indexing mark.
Between 2 of these supposedly isolated arcs there was a minimum of 3K
resistance, according to how I pressed them. I've removed one of the arcs
and there is now >30M bewtween both sides. It is associated with the tangs
that go between . The rotating paxolin disc is actually 2 discs and a I
suspect in the middle has acted capilliary fashion, taking in tar and
dampness and inside, between the 2 discs is a blackened cavern. Will remove
the next arc and see. The surfaces clean up quite well but replace the
tanged arc and a few 10s of K return.
no burnt cavity.
I assume these sorts of paxolin parts are formed under pressure in moulds.
Anyway they usually have a shiny varnish looking surface, like GRP gelcoat.
Inside , between the 2 discs, was quite clean and shiny except around each
hole where the metal tangs went through. Some sort of electrochemical
process surrounding each ,except the one with no metal passing through. A
ring about 1mm around each which looked as though the "varnish" coating had
lifted. The problem area was where 2 of these rings merged into 1.
HT3 monitoring , gradually dropped until the 1.2K dropper smoked.
Isoilated to problem in the dual canned C.
Restuffing dual 8uF, 350V electrolytic
Dated Oct 1946.
With a ball mill in Dremmel cut a ring, immediately inside the swaged rim,
into the black seal material. Then ground into the paxolin a small run,
enough to get some small parallel action jaw pliers in, to bend the swaging
back a bit and then moved around the rim in three attacks, to gradually open
back the rim. Pulled away the paxolin disc and then used an old wine-bottle
cork screw to remove the bulk of the fill. Lobster pick - a long
handle with 2 prong fork at one end and a small gouge
shaped spoon at the other both only about 1/4 inch wide, ideal for removing
most of the remainder after slight warming the can with hot air gun.
Then made a "tampon" out of tissue paper to pack into the can , seriously
heat up with hot air gun and then twirl the paper around with pliers to
clean out.
If I was doing this regularly I would get another set of these parallel
pliers and grind down to convex and concave faces, so as to leave little or
no nicks on the rim
Replacement modern caps are fine but how to replace the terminals as the
inside connection is either aluminium foil, aluminium wire or aluminium
rivet. Holes drilled through the paxolin to cary wires from the
inside to the original tags. 2 off 10uF, 450V covered
with some lengths of that sort of hosiery expandable mesh nylon
sleeving over each of the new caps before assembling together.
Sealing the disc in with green hotmelt so its
obviously not original and marking with date over
heat reflowed surface.
its easy opening back the rim but not losing metal to
contract it back so a scalloped retaining edge to the can.
Then powered up ok bit low level output and
distortion at higher levels.
0.1V , 400Hz , in gram input gave 0.46V over 2.3R
at output. Increasing to 0.15 , cross
over distortion and then negative waveform becoming more
and more triangular. Grid voltage 13V of V4 and
17V on V3 side of the 22K so decoupler cap failed.
Replaced with 47nF, 600V polyprop and also the
V4 anode cap with a large 2nF plate ceramic cap.
Now working properly and 0.1V , 400Hz , giving
0.46V over the speaker at full volume.
HT1 237V, HT2 209, next 193 and 190V in MW
and 241,214,207,194V as gram
Some DC (grid voltages not taken of topcapped ones) in gram
6K8 V1 0,0,243,0,0,0,0,0
6U7 V2 0,0,249,102,3,0,0,3 (6K7 on schematic)
6Q7 V3 0,0,110,0,1,8,0,1
6V6 V4 0,0,243,245,0,0,0,8
long wave
v1 0,0,195,-1,81,86,-,2
v2 0,0,200,87,0,-1,0,2
v3 0,0,75,0,0,11,0,0
http://home.graffiti.net/syxygy:graffiti.net/sobell_516a.jpg
Dexon bolted to rear to protect valves when inverted
and yellow cloth sticker for any later repairman
http://home.graffiti.net/syxygy:graffiti.net/sobell_516b.jpg
angled shot to pick up the sheen on the slats, original
dial cover had shrunk and dropped inside the cabinet.
http://home.graffiti.net/syxygy:graffiti.net/sobell_516c.jpg
http://home.graffiti.net/syxygy:graffiti.net/sobell_516d.jpg
At 250 V setting Tx 46R
Bulbs 1.9R and 2.1R , No 46 and No 40 labelled
Dial scale scan taken before and after cleaning
and main MW diameter length 138mm
Stringing - 3/4 around cap pulley and 2 turns
around main/reduction drive shaft.
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
Sony XR-C5300, car radio -failed tuner block
other than find a broken one or related model
also with the same tuner TUX-020 , any ideas?
Courtesy of some Danish and Polish threads someone found out that the 80 pin
Philips tuner IC TEA6842H is likely the same as the one badged Sony
8-759-653-23 in this tuner. All DC at the tuner 19 pins agree with Sony
Schema and rails, Xtal lines etc agree with the TEA... datasheet. There is
local Xtal osc, serial data and clock line signals on engaging "SEEK" ,
front display shows changing f but the TEA pin 42 tuning V stays at 0.045V.
Nothing amiss DVMing around the variable cap diode , pushing IC pins if
loose, and no bad ESR local caps. Whatever occured happened in a garage
during a cold spell of weather, vehicle rarely used.
Everything checked ,so far, pinning-wise has agreed with the TEA
datasheet and they are available but
a/ no confirmation that the Sony and TEA are the same
b/ desoldering 80 pin .5mm spacing IC is fine , it is the soldering in of
the new one I would be wary of, despite my express removal technique leaves
an alignment "ghost" in the original solder pattern.
20 turn 25K preset and 4K7 to the cathode of the varicap something like
BB156 marked F4 so probably HVC383B . AM and FM stations come in , so VCO
etc ok. Display showing bottom of the band of course. Another possibility is
corrupted serial link data between master controller and this TEA tuner IC
Incidently the radio data system works back to the display so even less
likely corrupted serial link going the other way.
Cutting my applied tuning voltage , the station goes off tune immediately.
I've not managed to get my head around the control system - a chicken and
egg situation ? Could a leaky varicap lead ,around the houses , to failure
to have an applied tuning voltage through the chain of VCO / PPL etc ?
Not same as XR C5200S
Remove front flap by pushing to the right and remove from the L pivot.
2+2+1 at topand R side bottom
2 ribbons remove and lift out cassette deck
Remove display panel , to test radio open , reinforce the ribbon for
reinsertion and a cable tie around each end to hold to the side panels,
wrap the reset sw to hold in
crystal osc ok
AM mode picks up local RF interference
CPout to C60
pin45 of TEA to pads between C59 and C54 nearest R20
First of these looked as though a failure of the tuner block. Owner bought
another one for spares, removable front display missing.
This one has exactly the same fault symptom so more likely a problem with
the front panel (or improbable same tuner fault on 2 separately acquired
units).
Tuner will go into auto strongest signal search and store in memory and also
readout follows manual input of frequency and stores in memory but at no
point does the audio come through to the output amp.
Pressing the presets shows the frequencies but no audio. Injecting local
modulated RF in there and audio is outputed and stays invariant on pressing
any preset so stuck on one RF tuning setting. So not a false muting problem
Some of the main chip SM solderings seemed suspect so redid the non LCD
segment ones. Cleaned the 14 pin front to interior header plug. No stuck
closed keys. It looks as though the front has been kneed at some point as
the ring around the rotary encoder button is cracked but no pcb problems
found.
The LCD clock, CE and data lines between the 14 pin header and the 64 pin
chip trace through. Not possible to scope anything on the board without
making up a one-off extender cable.
I'm assuming some data problem but what changes between sending data to and
from the tuner to load the presets and normal listening mode?
Schematics are out there for this model
I don't remember seeing this since the days of wired-in VCR remotes. A chain
of R varying from 680R to 10K for 11 of the main key switch sensing, not
diode array. That single resistance-set control line goes through the 14 pin
lift-off front panel connection to the main micro. Was thinking if outside
the allowed range, or dirty contacts, then perhaps an illegal mode, but they
check out true considering E12 series. High probability of a break somewhere
in such a chain of SM resistors.
Made a return with effects selection, with a standatd pot, on likes of
Roland Cubes.
One other person out there had this symptom ( unanswered)
"Im trying to fix an old car stereo, Sony XR-410. Cassette player works fine
but there is no sound in FM mode altough the frequency is displayed."
but as not a commonly reported fault I have to continue with front panel
fault cue
I did with the original one and you can manually tune via a 10 turn pot to
change stations with audio emerging from the pa. No reason to assume any
different with this one but as awkward to get to I will leave as is
Another possible variable is battery B+ but there is good regulation . With
no key presses the micro-sourced voltage is between 4.81V and 4.83V with no
power output , and invariant with "battery" between 12V and 14V
Measuring the keyed voltages , K-0, for the front buttons, pulls down to
left buttons 1.14,.60,.03V
central 1.50,.81,.33,2.57,3.69 V
right 1.83, 3.37, 3.00 V
I wonder what the acceptance bands for each of the 11 functions is in the
look-up table. I will guess at 1/3 of an interval with 1/3 for gaps for
unplaced or perhaps error so about .1V out and problems can ensue.
Will have to see if those voltages agree with the resistance chain, not
simple correspondence nor necessarily linear intervals. Minimum gap is .81 -
.6 V which looks suspicious at this stage. K-1 is similar resistance change
system for the other more minor function 8 buttons, I suppose I had better
check those also
unfortunately, including the .6 and .81V, all step V agree with scaling the
voltages of the resistance ladder on schema and reality, assuming a 10K
dropper inside the microcontroller.
Varying only about 20mV on any step
I don't know how this unit should function but this does not seem right.
Leave a tape in the unit and switch on with the front flap in place. Unit
recognises there is a tape inplace from initial jiggle. Then drives the tape
into the closed front flap , so slip clutch or whatever engages. "Nose
switch" , door switch , reset and tape present sw all function but what is
the point of sensing a tape present and sensing the door is closed and
trying to eject a tape into it. ?
I'd removed the tape deck and refitted but as confined space the controls
connector was refitted skew, it does now leave the tape in place at switch
on. I disabled the unused R/C receiver as that seemed stuck at 4.5v output
regardless of what random IR I fed to it, RS 170 chinese data out there.
Will reconnect and scope it properly today but am how at the Sherlock Holmes
stage
If you have eliminated all the possible then all that remains , however
unlikely, is the highly improbable - Same tuner fault with 2 randomly
obtained units.
I've just remembered I never checked the other A/D resistor chain for the
number buttons .
With the other chain , 4.83V V ref , you only have to add a pot and 100K or
so on the line to ground and bring that voltage down to 4.7V and that
disables any key sensing, whether it drops it to 3V or 0V on a key push. So
grime in the general sense could cause that symptom
Checking tape speed, for 1.875 ips using strobe etc (ITF)
Disconnect head ribbon and play upside down to strobe the capstan
Second deck with 12.55V supply 30.55 Hz (x4) = 1.880 for 1.99mm spindle
First deck 30.10 Hz = 1.852 ips
To avoid soldering rotary encoder for trying out front panel pad out with a cotton wool ball,
and 2 fingers only bent to hold to LCD section. 1 screw only near the nose sw.
D Bass LED designed to be on always, locate sw spigot in hole.
pin12 off
Hold the small plastic widget for mechanical latch, in place with some loose
hotmelt string or it will drop out at some point.
Monitor B+ at sw on , approx 4.8V then after 10 sec goes to 5.1V but press nose sw and so tape LED on
drops to 4.8V stays for 10 sec . So not a problem with LCD display driver loading the main board B+.
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.
Uher EG740 tuner from 1979 probably
Used every day,on FM, until one day, switching on and very low level audio out. Tuning is fine on FM and AM is normal. Phono and Aux inputs to amplifier are normal. Schematic on elektrotanya. Nothing loose found on twizzling. There are some ceramic resonator filters, I'm aware of silver migration over such time spans , resulting in attenuation of throughput, anything else to zero-in on?
Lots of Din connectors connecting tuner to preamp and amp, power , signal and control connections. Any advice on improving contacts other than needle insertion to tension up the socket yokes a bit.
Uses 4x 10.7M ceramic resonators, the resistance associated with 2 of them , is from the rest of the circuitry
Looks like it was a retrofit electrolytic to a 9.4V line, with a large component side solder blob that had corrossion product that touched a bare bridge wire from the mute line of the main control IC.
Remove 4x stickers to remove 4x sc, 1 had sputtered metal
anti-tampering?
front panel 3 long ms, if wiring should break , order is
Bn+W,R,bk+bk,gy, or,blue,or
2 sc other side of display to release whole display driver box
in to out of F2 >30M
F3 >30M
f4 850 to gnd
yellow cs6 wire broke from retrofit cap at the diodes, not obvious break
at pcb.
Put some temp insulation under small front pcb as now loose.
No stereo red LEDon any station , blips red at switch on.
replaced the buff ceramic 10.7m filters, no change
presets values
FMsig 12.7K
sepa 15K
amsig 441R
am ant 2.83K
F8 not found , renumbered?
F8=F7 ?, F7=F6 ?
VRef2 7.98V, next to it 9.4V
4xaaa NimH cells with heatshrink replaced the original cells,
hot melted into tight space.
Replace display box, replace 2 side sc but loose,
replace middle front sc then tighten the 2 sc
Return of same problem , lowish o/p and no stereo in AFC posistion
near enough drops out totally , multipath pos no different.
Insulated barrel pushed in small area between FMsig
and F5 changes from good to bad output.
1uF good ESR
pin13 of IC2 and T6
Regelspannung 5V on schematic, 4.88V here
p13 is Smeter o/p , from Sony STR V4 manual
good DC readings for pin 2,12,13
4.88,varying,1.34
bad 2.0,5.6,.02V
Changing F1 setting , after marking, only worsens
UPC1167 p1 and p2 looks as though should
be both 1.8V to 2V but 4.88V when bad, try 82K to gnd
1.74V on p1 and p2 now, strong mono out, no stereo and sw
to AFC and signal goes.
Tried 1 Meg and 1.95V to p1 and p2 and 1 or 2 stereo channels come up. After 5 minutes 5 come stereo come in.
Settled on 3.3M 1.99 to 2V
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
Telephone number - the same number as it has been since 1988
but email is now the preferred method of contact so number deliberately not placed here.
I devote time each day to replying to emails.
(obscure/obsolete components,second hand test equipment,
schematics etc)
Postal: 66 Ivy Rd,St Denys,Southampton,England SO17 2JN
There is no point in contacting me about any of the above, the
repair job may have been done 15 years ago .
I cannot clarify or enlarge on any of the above.
e-mail
A reserve email account is diverse9(commercial at)fastmail.fm.
Please make emails plain text only , no more than 5KByte or 500 words.
Anyone sending larger texts or attachments such as digital signatures, pictures etc will have
them automatically deleted on the server. I will be totally unaware of this - sorry, again
blame the spammers.
More hints & tips and repair briefs on
homepage http://home.graffiti.net/diverse:graffiti.net/
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