Hello,
I have a Philips Cd101 with no sound. I believe the issue is with power regulator LM337MP which is 6224 in service guide.
All 3 legs measure -5.1.
Leg 1 should = -16.6
Leg 2 should = -31v
Leg 3 Should = -18v
All other power supply Regs measure to spec.
Subsequently both TDA1540 Dacs are missing the -18v supply on Pin 11 and the -13v on Pin8 and Pin 9.
There may be other issues but this is the most obvious.
All caps are new.
Hoping someone can give me a hand here😀.
Thanks
I have a Philips Cd101 with no sound. I believe the issue is with power regulator LM337MP which is 6224 in service guide.
All 3 legs measure -5.1.
Leg 1 should = -16.6
Leg 2 should = -31v
Leg 3 Should = -18v
All other power supply Regs measure to spec.
Subsequently both TDA1540 Dacs are missing the -18v supply on Pin 11 and the -13v on Pin8 and Pin 9.
There may be other issues but this is the most obvious.
All caps are new.
Hoping someone can give me a hand here😀.
Thanks
Diode BAW62 is also measuring -5.1v and I believe that comes before the LM337 in the chain, but I might be wrong.
Likely it is in "anti parallel" with the 337, to discharge the output capacitor when powered down.
Diodes 6266 and 6268 are not measuring any voltage. Not sure if i should be getting a reading but it's really low like -.03v. And these diodes are in the same chain but further in front of the power supply chain. Diode 6267 is the one measuring -5.1v.
So I installed a fresh LM337 Regulator and still same results. All 3 legs measure between -5.1v to -5.4v.
Hmmm. Maybe something downstream of the 337 is shorted, pulling everything down. The regulator may not be bad,
just in current limiting. Do you have a schematic?
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Yeah I have a schematic...
I know its in the audio signal. I measured the 5532 amps, the both get +12/-12 on pin 4 and pin 8. Now according to the schematic pin 1, 5, 7 should read 3.4v, instead its reading -10.56v on all 3 pins on 1 5532 chip, while the other one is getting 3.54v on the same 3 pins. Its the 5532 chip that is marked 6525 in the schematic. And all the resistors and golden caps measure -10.56v as well.
Too much information I know.🙁
I know its in the audio signal. I measured the 5532 amps, the both get +12/-12 on pin 4 and pin 8. Now according to the schematic pin 1, 5, 7 should read 3.4v, instead its reading -10.56v on all 3 pins on 1 5532 chip, while the other one is getting 3.54v on the same 3 pins. Its the 5532 chip that is marked 6525 in the schematic. And all the resistors and golden caps measure -10.56v as well.
Too much information I know.🙁
UPDATE..😀
So I traced 2 faulty diodes that come before the LM337. 1 was open circuit and 1 and was short circuit. Also, one of the tiny red wires had come undone from the transformer and was touching another wire. This is what probably caused the short.
Now the Lm337 has correct reading and so do all the TDA 1540 pins.
But still no sound! Reason I'm assuming has a lot to do with the fact they are getting -10.56v readings instead of 3.4 on pins 1, 5, 7. They are both reading +12/-12 on pins 4 and 8.
Any ideas would help.
Ray thanks for all your help and suggestions.
So I traced 2 faulty diodes that come before the LM337. 1 was open circuit and 1 and was short circuit. Also, one of the tiny red wires had come undone from the transformer and was touching another wire. This is what probably caused the short.
Now the Lm337 has correct reading and so do all the TDA 1540 pins.
But still no sound! Reason I'm assuming has a lot to do with the fact they are getting -10.56v readings instead of 3.4 on pins 1, 5, 7. They are both reading +12/-12 on pins 4 and 8.
Any ideas would help.
Ray thanks for all your help and suggestions.
Sorry about all your trouble, what the heck happened to this player, anyway? Can you post a schematic?
It was playing fine for years. My guess is the tiny red wire had a strand or 2 come undone and made contact with one of the other wires and BAMM. Now I have it confined to the audio circuit area. I know the op-amps are not getting proper voltage and 2 of the caps in the audio signal path are getting 0v to very low voltage like .68v. attached is the decoder board. The caps not getting any voltage are are marked with a red marker. They are 2608 and 2573 on the schematic.
Attachments
If it were me, I'd try replacing the dual op amp in the bad channel. Maybe the D/A in that channel is still good, and that might fix it.
Neither channel is working. I'm thinking it has to be something that is controlling both channels, for example 2 parallel resistors that might be open. I don't wanna unsolder and solder willy nilly.
Then it's somewhat likely that it's the power supply, unless all the ICs are damaged. Can you post the complete schematic, or a link?
All the power supplies rails are spot on. And all the power coming up to Decoder board 2 are spot on, its once they get past the resistors and such that problems arise. You can download manual here.http:
//elektrotanya.com/philips_cd101-00-05_sm.pdf/download.html
//elektrotanya.com/philips_cd101-00-05_sm.pdf/download.html
Could it be the "kill" output muting relay not energizing? It's normally off. The two channels are unlikely to have the identical problem,
so it is almost certainly a single, common problem.
Does the player spin up and read CDs at PLAY command? If yes, then everything before the DAC (decoder, filter and system clock) are healthy. Try playing a test CD with sine wave signal measurable with a DMM and trace the analogue signal path from output backwards.
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It spins up just fine, reads TOC, plays the disc and all functions work. One channel you can hear audio very faintly with a lot of hiss, other channel is silent.
My test equipment is limited to an ESR tester, capacitor tester, multimeter and common sense😀.
My guess is since the -18v was missing from earlier and having those 2 diodes go short in the power supply, it must be something further up along the same line. All the voltages are correct now except on the Op-amps. The op-amps are reading +12/-12 on pins 4 and 8. Except one of them is reading -10.56v on pins 1,5,7, when in fact it should be +3.4v. The other op-amp rises to +3.4v on the same pins and then voltage declines to -1.2v.
My test equipment is limited to an ESR tester, capacitor tester, multimeter and common sense😀.
My guess is since the -18v was missing from earlier and having those 2 diodes go short in the power supply, it must be something further up along the same line. All the voltages are correct now except on the Op-amps. The op-amps are reading +12/-12 on pins 4 and 8. Except one of them is reading -10.56v on pins 1,5,7, when in fact it should be +3.4v. The other op-amp rises to +3.4v on the same pins and then voltage declines to -1.2v.
You need AC 2V range on DMM in order to follow the signal path in the way I described. Try playing 1kHz 0dB test signal and you should read approx. 1V on your meter after op amps.
If reverse voltage pulldowns you mentioned in earlier posts did not kill one or both DACs, then there's hope. Are opamps overheating? Try removing them and see if you can get correct rail voltages. Also, see if the test signal is reaching inputs on op amps.
If reverse voltage pulldowns you mentioned in earlier posts did not kill one or both DACs, then there's hope. Are opamps overheating? Try removing them and see if you can get correct rail voltages. Also, see if the test signal is reaching inputs on op amps.
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