Hi,
Not my first player of that generation (1983). I’ve already done quite a few over the years.
But that one… 😓
Does anybody here know what the issue might be?
This is a SO-PHI model.
The reed relays are fine.
CDs are read but no sound – it worked just a week ago!
The player has just been repaired by myself. Prior to repairs, the player didn’t play anything, didn’t display anything.
I have the full service manual, checked everything on the oscilloscope and yet no sound (both channels).
Eye pattern looks absolutely perfect, if you are wondering, and all functions work.
All I can hear is a click when track changes.
Op-amps are fine.
Any leads welcome.
Thanks for looking! This picture was shot before the repairs. DIL sockets have also been replaced.
Not my first player of that generation (1983). I’ve already done quite a few over the years.
But that one… 😓
Does anybody here know what the issue might be?
This is a SO-PHI model.
The reed relays are fine.
CDs are read but no sound – it worked just a week ago!
The player has just been repaired by myself. Prior to repairs, the player didn’t play anything, didn’t display anything.
I have the full service manual, checked everything on the oscilloscope and yet no sound (both channels).
Eye pattern looks absolutely perfect, if you are wondering, and all functions work.
All I can hear is a click when track changes.
Op-amps are fine.
Any leads welcome.
Thanks for looking! This picture was shot before the repairs. DIL sockets have also been replaced.
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When you say you checked everything on the scope, what do you mean? Reason I ask is because if no sound then some signal or other would probably not look right on a scope. Like for instance, are there audio signals coming out of the dac chips? If not, are there digital signals going into the dac chips, etc.? Something has to look wrong somewhere doesn't it?
Thanks. No, nothing gets out of both DAC chips. Nothing gets in either!
Hence the question about muting, which I fail to understand or test.
Hence the question about muting, which I fail to understand or test.
Okay. Service manual presumably has schematics. The usual thing would be to see if there is troubleshooting advice or steps given in the manaual. If not, then maybe start looking at some digital scope signals that should be present before going into the dac chips. In other words, there is a signal path from input to output. The optical reader is the audio input source. If it and the servos are reading valid data then you should see data streaming along in digital format towards the dac chips. Maybe there are some waveforms shown on the schematic? If its not loading, tracking, etc. -- the stuff that has to happen first before data can reliably be read from the CD, then start looking at the process and signals there. One approach to troubleshooting is signal tracing, following a signal as it is input and processed all the way until it gets to the output. Something won't look right on the scope somewhere along that path. The other thing in this case is the process or sequence of things that has to happen to load the CD and read it. If you know what's supposed to happen then you check along the way to see where its not happening. That kind thing, if that makes sense. The idea as this point is to try to localize where in the system something is not right. The earliest thing wrong in the signal or process flow is what you want to find. Usually the problem is right around there.
Yes, I know. I have the manual but I can’t trace the signal correctly because the manual refers to the Philips chipset. Here I have a Sony chipset.
The service manual is not really helpful, unfortunately. I don’t know where to start to be honest.
All I know is that CDs play, the eye-pattern looks good and every test point I’ve come across looks like the ones in the manual.
There’s nothing about the DAC or the audio side in the SM. Only servo anomalies are referred to.
What else can I do?
The service manual is not really helpful, unfortunately. I don’t know where to start to be honest.
All I know is that CDs play, the eye-pattern looks good and every test point I’ve come across looks like the ones in the manual.
There’s nothing about the DAC or the audio side in the SM. Only servo anomalies are referred to.
What else can I do?
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Found a little info on the Sony CX7934 chip.
EDIT: It sounds like you don't actually have THE service manual for this particular unit?
EDIT: It sounds like you don't actually have THE service manual for this particular unit?
Attachments
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I do, but I can’t find anything on the special module and what it should exactly do!
What is SMSE?
What is SMSE?
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Info on the CX7934? CX7935? Just for that one PCB?
EDIT: Regarding SMSE, where does it go to on the decoder board? Is there some clue there? It goes into an input pin on CX7934 named MUTG. That might suggest it could be a mute signal. If so, the E in SMSE might suggest an Enable signal?
Maybe all you can do is look at the voltage an SMSE with no CD, CD inserted but not playing, when it is supposed to be playing, etc. If SMSE never changes state, then maybe that could be a clue that the decoder board is having some problem. Its a detective puzzle that you may or may not be able to solve. Having a working unit to compare with might allow you to become expert on it.
Another thing you might try could be to force MUTG into another state and see if anything else changes, say, maybe if you get output but its some kind of noise or garbled audio. Of course, that's something only to consider trying if nothing else is working and you don't think changing MUTG state is likely to break anything worse than it is already. You know?
EDIT: Regarding SMSE, where does it go to on the decoder board? Is there some clue there? It goes into an input pin on CX7934 named MUTG. That might suggest it could be a mute signal. If so, the E in SMSE might suggest an Enable signal?
Maybe all you can do is look at the voltage an SMSE with no CD, CD inserted but not playing, when it is supposed to be playing, etc. If SMSE never changes state, then maybe that could be a clue that the decoder board is having some problem. Its a detective puzzle that you may or may not be able to solve. Having a working unit to compare with might allow you to become expert on it.
Another thing you might try could be to force MUTG into another state and see if anything else changes, say, maybe if you get output but its some kind of noise or garbled audio. Of course, that's something only to consider trying if nothing else is working and you don't think changing MUTG state is likely to break anything worse than it is already. You know?
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There are three Sony chips here.
Maybe it’s a simple thing but I don’t know what to look for.
Maybe it’s a simple thing but I don’t know what to look for.
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Well, some of the signals look like clocks and data, more or less similar to I2S type digital audio. Are those signals there, do they change when you try to play a CD? What do the other signals do, do they ever change? Where do those signal go to on other boards? Do you have information on the other boards to figure out what the signals might be for?
I do. I always go back to the Sony module though, and that muting thingy that shows absolutely nothing. Mute seems to be always high.
Its obviously an input to the CS7934 since it goes through an inverting buffer. Signal can only pass through there in one direction. Therefore if its a problem, the problem is probably not being generated on this board. Must be the board that feeds it, or something before that. Have to work backwards to look for more clues.
The little arrows going in and out of MAB8440PB show signal flow direction. It only has so many inputs. Any idea what those are?
The Sony chipset is the one at centre : ERCO/RAM controller. I tried cutting the muting voltage but it does absolutely nothing.
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Ok, so when the player is idle, we have SMSE (muting signal) at 4.5 V, turning to zero when a track is being played. Fair enough.
We also have a constant zero at the other side of the inverter: we should find 4.5 V when a track is being played, thus triggering the signal output. Correct?
It looks as if the Texas SN74LS04N on the Sony board might be dead. It is powered obviously.
Any thoughts?
We also have a constant zero at the other side of the inverter: we should find 4.5 V when a track is being played, thus triggering the signal output. Correct?
It looks as if the Texas SN74LS04N on the Sony board might be dead. It is powered obviously.
Any thoughts?
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Okay. At least more is known now. Not sure if you want to focus on the dac board or somewhere else. If the former, what I might do is collect datasheets for everything on the board I can. Then I would remove the board and sketch out a schematic from visual examination. Since pinouts of the dac chips and some of the other chips are known, it may be possible to infer which pins are inputs and outputs on undocumented chips. Eventually it may be possible to more fully analyze the circuit to aid troubleshooting. Maybe at least start sketching the digital signals coming into the board and making their way to the dac chips after passing through other chips on the board. Does that sound like something you would be willing to do?