You can reassemble without grease to try it. Some even recommend leaving it like that although I wouldn't personally. The grease can be applied later (use very sparingly on the gears and a tiny smear on the friction points on the rail and the frame that the other side of the pickup "rubs along" on)
Hi all,
I have completely dismantled, inspected and cleaned rails and gear(s) on the laser mechanism. While there, i did a comparison with parts of a spare cd63. There are subtle differences with the 63ki having the laser mounted on a steel rail held in place on each end by two slip-in plastic lugs. There are also what looks like pieces of nylon or plastic tube (dampers) on each end of the steel rail. The cd63 simply has the rail placed into the plastic body with a philips screw locking it down. Here is what I tried:
- swapped laser drive motors - problem persists
- swapped mounting body and inspected and reseated mounting rubbers - no change
- last resort was to try my CD67 MkII in the CD63KI - no read, no toc, just 'disc'
The only thing I haven't tried is adjusting the laser.
Replacing the laser mechanism with a new one may be the last resort.
I have completely dismantled, inspected and cleaned rails and gear(s) on the laser mechanism. While there, i did a comparison with parts of a spare cd63. There are subtle differences with the 63ki having the laser mounted on a steel rail held in place on each end by two slip-in plastic lugs. There are also what looks like pieces of nylon or plastic tube (dampers) on each end of the steel rail. The cd63 simply has the rail placed into the plastic body with a philips screw locking it down. Here is what I tried:
- swapped laser drive motors - problem persists
- swapped mounting body and inspected and reseated mounting rubbers - no change
- last resort was to try my CD67 MkII in the CD63KI - no read, no toc, just 'disc'
The only thing I haven't tried is adjusting the laser.
Replacing the laser mechanism with a new one may be the last resort.
slipped up..
I 'blew' FH10 and FH11,
fortunately I have a box of them in my spare parts bin - replaced both and cdp is active again with full display. I need to be extra careful in future.
Moving on to the laser testing:
I tried something different this time, playing a few seconds of every track on a cd - ie - track 1 fwd to track2 all the way to track 12. I found that every track was read by the laser and played. However, if any track was left to play to the end - invariably audio would cut out. The longer the track was left to play the shorter the time it took to cut out. Track 1 would take up to 15 minutes of uninterrupted audio thereafter audio would cut out. After resuming play audio would cut out after 3 to 5 minutes.
The service manual schematic identifies 3 beams active in the laser. Is it possible for one of the beams to fail? Which would explain why the cd is being read, and the TOC is displayed as is the timer etc on the display.
Is it possible that one of the three beams is responsible for transfer of digital to audio signals and that is the one that is on it's way out?
OR does the laser work on a all or nothing principal?
Kindly excuse my 'untrained logic' in trying to make sense of the problem.
I 'blew' FH10 and FH11,
fortunately I have a box of them in my spare parts bin - replaced both and cdp is active again with full display. I need to be extra careful in future.Moving on to the laser testing:
I tried something different this time, playing a few seconds of every track on a cd - ie - track 1 fwd to track2 all the way to track 12. I found that every track was read by the laser and played. However, if any track was left to play to the end - invariably audio would cut out. The longer the track was left to play the shorter the time it took to cut out. Track 1 would take up to 15 minutes of uninterrupted audio thereafter audio would cut out. After resuming play audio would cut out after 3 to 5 minutes.
The service manual schematic identifies 3 beams active in the laser. Is it possible for one of the beams to fail? Which would explain why the cd is being read, and the TOC is displayed as is the timer etc on the display.
Is it possible that one of the three beams is responsible for transfer of digital to audio signals and that is the one that is on it's way out?
OR does the laser work on a all or nothing principal?
Kindly excuse my 'untrained logic' in trying to make sense of the problem.
Bet your relieved it was just a couple of fuses
The three beam pickup derives all the "beams" from a single laser diode by splitting the light with a diffraction grating. Although the laser diode won't cause a problem with individual "beams" the photo diode array that the light makes its way back to after being reflected off the CD can suffer with problems.
I honestly don't know what to suggest. I think your getting to the stage where you have to try a new pickup.
My approach now would be a dual beam scope, one channel to monitor the RF and the other to look at the DC drive to the sled. If that showed nothing I would start to look and check everything. DC rails to all the IC's, again looked at on a scope. We've covered all the basics and not fixed it so now any fault finding has to get much more involved looking at what changes when this fault appears.
You might be lucky and find a new pickup fixes it but without really detailed tests I wouldn't guarantee it...
The three beam pickup derives all the "beams" from a single laser diode by splitting the light with a diffraction grating. Although the laser diode won't cause a problem with individual "beams" the photo diode array that the light makes its way back to after being reflected off the CD can suffer with problems.
I honestly don't know what to suggest. I think your getting to the stage where you have to try a new pickup.
My approach now would be a dual beam scope, one channel to monitor the RF and the other to look at the DC drive to the sled. If that showed nothing I would start to look and check everything. DC rails to all the IC's, again looked at on a scope. We've covered all the basics and not fixed it so now any fault finding has to get much more involved looking at what changes when this fault appears.
You might be lucky and find a new pickup fixes it but without really detailed tests I wouldn't guarantee it...
The three beams are derived optically from a single laser diode. An array of photodiodes picks up the reflected light. Several centre-beam pds, in your case three, are are AC-coupled in parallel to form the signal which, after amplification with the HF amp, becomes the data signal to the decoder chip. That data signal is the one that should appear as an eye pattern on a scope. Those three pd signals also go to the TDA1301 servo processor, together with two others that I assume follow the other two beams. All the control signals for the mechanism are derived from sum-and-difference hocus-pocus comparing the signals from the various pds.
So, most of the functionality of the head can be observed in the eye pattern, which is why it's such an important indicator. Without a scope, it won't be easy to tell which of the various devices involved is misbehaving.
When you say that the audio cuts out, do you mean that the player continues to track the disk? Does the display show progress through the disk as if it were playing
The varying times before audio is lost suggests the problem may be temperature related.
There's a diagram (with one more pd than yours) and lots of info here:
Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives
So, most of the functionality of the head can be observed in the eye pattern, which is why it's such an important indicator. Without a scope, it won't be easy to tell which of the various devices involved is misbehaving.
When you say that the audio cuts out, do you mean that the player continues to track the disk? Does the display show progress through the disk as if it were playing
The varying times before audio is lost suggests the problem may be temperature related.
There's a diagram (with one more pd than yours) and lots of info here:
Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives
I tried the freezer spray on various components including ICs on the pcb and the change in temperature did not result in any audio output.
Your question: "When you say that the audio cuts out, do you mean that the player continues to track the disk? Does the display show progress through the disk as if it were playing"
Answer: During play, the cd will play as per normal, toc timer track recogntion etc. And audio. But this will go on for approx 10 - 15 minutes the audio will cut out. Cd continues spinning, timer continues and the laser mechanism can be seen to be moving toward the rear of the tray ie it is not fixed or 'stuck' on any tracks.
Your question: "When you say that the audio cuts out, do you mean that the player continues to track the disk? Does the display show progress through the disk as if it were playing"
Answer: During play, the cd will play as per normal, toc timer track recogntion etc. And audio. But this will go on for approx 10 - 15 minutes the audio will cut out. Cd continues spinning, timer continues and the laser mechanism can be seen to be moving toward the rear of the tray ie it is not fixed or 'stuck' on any tracks.
Lets try and look at this from another angle (and I'm saying this because without actually seeing for myself exactly what is happening its all becoming a bit guess work)
The TOC advances correctly and the player "seems" OK apart from the audio dropping out.
A player where the RF has a problem causing the audio to stutter and yet the TOC to work is a knife edge situation, so is it probable or likely that is happening. Lets say no. What are we left with. Without hearing and seeing the fault, again its guesswork but harsh "digital" sounding hash is often caused by faulty DRAM memory (in older players) but I've never had the problem on the combined DAC/MEMORY/PROCESSING chips. Doesn't mean it doesn't happen though.
As a totally off the wall suggestion try disabling the audio muting in the analogue stages and see what that does.
I think beyond this and we have to accept that its not a diy prospect without the right test gear and so on.
The TOC advances correctly and the player "seems" OK apart from the audio dropping out.
A player where the RF has a problem causing the audio to stutter and yet the TOC to work is a knife edge situation, so is it probable or likely that is happening. Lets say no. What are we left with. Without hearing and seeing the fault, again its guesswork but harsh "digital" sounding hash is often caused by faulty DRAM memory (in older players) but I've never had the problem on the combined DAC/MEMORY/PROCESSING chips. Doesn't mean it doesn't happen though.
As a totally off the wall suggestion try disabling the audio muting in the analogue stages and see what that does.
I think beyond this and we have to accept that its not a diy prospect without the right test gear and so on.
Apologies for repeating Mooly...written so sending anyway.
At the start of the thread, there was some skipping and response to tapping the mech. Have these aspects disappeared?
I'm still trying to learn about this stuff and my experience is of machines a generation before yours, so I might be wrong...
Your mech must be focusing and tracking otherwise it couldn't do what it's doing, music or not. Further, the signal from the HF amp to the decoder (that should appear as the eye pattern) must be good enough to decode for the player to navigate itself. The music data and the subcode are read from the disc, carried on the same signal, and decoded by the same decoder chip.
One thing you can check easily with a multimeter is the mute signal.
Without a scope, I would use a CD with a simple signal such as a full-scale 1kHz sine wave, assuming the machine can read CDRs, so then I could follow it back through the audio stage with the meter set to AC volts, looking at the output of each opamp, and the DAC if it's voltage output. When the audio is working and when it's not.
If the output from the DAC (or the I/V stage) disappears, then you are left with the decoder chip, the digital filter, or the DAC. I would check for cracked pins or poor solder joints, but they can be hard to spot even with a magnifying glass. Others may be able to comment on whether the health of digital signals can be interpreted with a multimeter. Tricky, I would have thought.
15 minutes is a long time. For it to be heat related, it would have to be somewhere that gets hot very slowly, and only in the presence of audio. An encapsulated class B audio stage perhaps, or it's power supply. Does it just vanish, or fade, or what? Intriguing, don't give up.
At the start of the thread, there was some skipping and response to tapping the mech. Have these aspects disappeared?
I'm still trying to learn about this stuff and my experience is of machines a generation before yours, so I might be wrong...
Your mech must be focusing and tracking otherwise it couldn't do what it's doing, music or not. Further, the signal from the HF amp to the decoder (that should appear as the eye pattern) must be good enough to decode for the player to navigate itself. The music data and the subcode are read from the disc, carried on the same signal, and decoded by the same decoder chip.
One thing you can check easily with a multimeter is the mute signal.
Without a scope, I would use a CD with a simple signal such as a full-scale 1kHz sine wave, assuming the machine can read CDRs, so then I could follow it back through the audio stage with the meter set to AC volts, looking at the output of each opamp, and the DAC if it's voltage output. When the audio is working and when it's not.
If the output from the DAC (or the I/V stage) disappears, then you are left with the decoder chip, the digital filter, or the DAC. I would check for cracked pins or poor solder joints, but they can be hard to spot even with a magnifying glass. Others may be able to comment on whether the health of digital signals can be interpreted with a multimeter. Tricky, I would have thought.
15 minutes is a long time. For it to be heat related, it would have to be somewhere that gets hot very slowly, and only in the presence of audio. An encapsulated class B audio stage perhaps, or it's power supply. Does it just vanish, or fade, or what? Intriguing, don't give up.
This might interest you as a general guide to working through a problem,
http://www.diyaudio.com/forums/digi...0-kss240-restoration-project.html#post3296233
Update on the challenge guys...
First off, don't know how to disable the muting on the player - but i think part of the mods required attention to the muting section. or disabling it ( I do know that I have to turn the cdp on first and then the amp) to prevent a popping sound..
I had a think about an alternative approach while still trying to source a scope again.
The uneducated logic being - if i use an external DAC and the fault disappears then it is the audio/dac section. If the problem is still evident with an external DAC then the problem may well be the laser pick up. ( I am aware that it may be more complicated than my description). However, I tried the coax to an av amp and this did not work at all - the word DISC was displayed, no spin up and no TOC!!!
I removed the coax and powered up and the cd spun and toc display popped up immediately.
OK! is the problem linked to Coax?? Too difficult to consider..
So I moved to the next option (Optic output option) plugged into my AV amp and it played BUT while the cd produced audio through all the tracks - however, it produced shorter audio output times ie played for 10-15 seconds and audio dropped out for a second or second and a half and audio kicked in again and this went on for about 25 minutes or 5 tracks then audio cut out altogether. I switched back to analogue and the same problem persists ie - plays for 10 -15 mins drops out completely then after 10 mins continues playing -
This is interesting - with analogue output - audio plays for 25minutes and drops out completely. Using the optic output, the audio dropouts were more frequent and significantly shorter, with audio continuing after 1.5 seconds or less. We may have to rethink the heating possibility.
First off, don't know how to disable the muting on the player - but i think part of the mods required attention to the muting section. or disabling it ( I do know that I have to turn the cdp on first and then the amp) to prevent a popping sound..
I had a think about an alternative approach while still trying to source a scope again.
The uneducated logic being - if i use an external DAC and the fault disappears then it is the audio/dac section. If the problem is still evident with an external DAC then the problem may well be the laser pick up. ( I am aware that it may be more complicated than my description). However, I tried the coax to an av amp and this did not work at all - the word DISC was displayed, no spin up and no TOC!!!
I removed the coax and powered up and the cd spun and toc display popped up immediately.
OK! is the problem linked to Coax?? Too difficult to consider..
So I moved to the next option (Optic output option) plugged into my AV amp and it played BUT while the cd produced audio through all the tracks - however, it produced shorter audio output times ie played for 10-15 seconds and audio dropped out for a second or second and a half and audio kicked in again and this went on for about 25 minutes or 5 tracks then audio cut out altogether. I switched back to analogue and the same problem persists ie - plays for 10 -15 mins drops out completely then after 10 mins continues playing -
This is interesting - with analogue output - audio plays for 25minutes and drops out completely. Using the optic output, the audio dropouts were more frequent and significantly shorter, with audio continuing after 1.5 seconds or less. We may have to rethink the heating possibility.
Good thinking to try an external DAC.
The coax thing is really odd and I wouldn't expect that to happen. Only two possibilities there, one is that the coax feed is unbuffered (surely not) and connecting it to the DAC kills or reduces the level internally in the player such that it throws a fit. That the coax feed should be configured like that is too unlikely to contemplate... although you mention mods haveing been done. The other thought which is even more unlikely is that there is some bizzarre short occuring via the coax and the equipment grounds.
Normally the coax feed of the SPDIF signal is via a tiny "pulse" or HF transformer to make it imune to whatever the "customer" connects or does to the output. I would have to see the circuit to see how its configured but what you describe sounds totally odd. I would say that was worth investigating.
The optical output vs the analogue output differences may just be down to the different signal processing each DAC uses and when it sees fit to mute the audio. I wouldn't read to much into that other than it seems to point to a front end problem.
The coax thing is really odd and I wouldn't expect that to happen. Only two possibilities there, one is that the coax feed is unbuffered (surely not) and connecting it to the DAC kills or reduces the level internally in the player such that it throws a fit. That the coax feed should be configured like that is too unlikely to contemplate... although you mention mods haveing been done. The other thought which is even more unlikely is that there is some bizzarre short occuring via the coax and the equipment grounds.
Normally the coax feed of the SPDIF signal is via a tiny "pulse" or HF transformer to make it imune to whatever the "customer" connects or does to the output. I would have to see the circuit to see how its configured but what you describe sounds totally odd. I would say that was worth investigating.
The optical output vs the analogue output differences may just be down to the different signal processing each DAC uses and when it sees fit to mute the audio. I wouldn't read to much into that other than it seems to point to a front end problem.
Helpful, thanks. Knowledge is social, and it's reassuring to see that my rather isolated efforts to learn aren't so far away from professional practice. I'm impressed by your twiddlesticks. Having fixed quite a few early players since arriving in the digital era this year, I just had my first accident, blowing up a CD50 with a screwdriver.
Compared to Philips single beam mechs, Sony and Philips CDM12 machines seem very fidgety, and get mechanically noisy, apparently beyond the range of adjustment. Ringing, over-hard plastic doesn't help. It's a pity Sony doesn't explain the "correct" method of adjustment. Presumably it allows the system poles and zeros to be optimally spread. I find the two nested subsystems for tracking control hard to get my head around.
Returning to the matter in hand, I think we're stumped for lack of data. If the problem's not in the audio section, then without a scope I'd be doing what I like least: patiently logging the DC and AC voltages on lots of pins. The cause of completely lost audio should be obvious somewhere, if the machine is otherwise working normally.
Compared to Philips single beam mechs, Sony and Philips CDM12 machines seem very fidgety, and get mechanically noisy, apparently beyond the range of adjustment. Ringing, over-hard plastic doesn't help. It's a pity Sony doesn't explain the "correct" method of adjustment. Presumably it allows the system poles and zeros to be optimally spread. I find the two nested subsystems for tracking control hard to get my head around.
Returning to the matter in hand, I think we're stumped for lack of data. If the problem's not in the audio section, then without a scope I'd be doing what I like least: patiently logging the DC and AC voltages on lots of pins. The cause of completely lost audio should be obvious somewhere, if the machine is otherwise working normally.
Yes, good idea to check the digital out.
The audio mute signal should be quite easy to find and very easy to check. It goes to the mute section and changes state before and after each track. I assume you have a circuit diagram?
If the machine has a chip that combines digital filter and SPDIF encoding, I would check around there, especially if the circuit has been modified, obviously. It could be that the modification has caused, or is causing the problem, by overheating part of the chip or its power supply, or upsetting its clock.
It seems to me more likely now that the problem is about failure to process the digital signal, rather than a rogue mute signal. AFAIK, everything up to and including the decoder has a part in controlling the mech, so if the mech is well behaved the problem must be after that, and before the encoding of the digital output. There's only the filter chip, unless an improper system microcontroller is intervening very strangely.
Mooly, what's a "front end problem", and what points to that? Can it intervene in such a way as to generate a mute signal that goes to the digital output?
An overheating chip may degrade the signal in a way that is interpreted differently by each system. Something must be responsible for explaining the timing of each transition from on state to another.
Hoping I'll be in sequence this time....
The audio mute signal should be quite easy to find and very easy to check. It goes to the mute section and changes state before and after each track. I assume you have a circuit diagram?
If the machine has a chip that combines digital filter and SPDIF encoding, I would check around there, especially if the circuit has been modified, obviously. It could be that the modification has caused, or is causing the problem, by overheating part of the chip or its power supply, or upsetting its clock.
It seems to me more likely now that the problem is about failure to process the digital signal, rather than a rogue mute signal. AFAIK, everything up to and including the decoder has a part in controlling the mech, so if the mech is well behaved the problem must be after that, and before the encoding of the digital output. There's only the filter chip, unless an improper system microcontroller is intervening very strangely.
Mooly, what's a "front end problem", and what points to that? Can it intervene in such a way as to generate a mute signal that goes to the digital output?
An overheating chip may degrade the signal in a way that is interpreted differently by each system. Something must be responsible for explaining the timing of each transition from on state to another.
Hoping I'll be in sequence this time....
Good aren't they
I have a "proper" diffraction grating adjustment tool for some pickups too. Now that is fun (read nearly impossible) trying to adjust that while playing. Fortunately most pickups never need it.Blowing something up happens to the best. We've all been there
Generally speaking a "good" pickup is very tolerant of mis alignment. If the adjustments seem super critical to get it to play and track then usually there is some underlying issue. The proper alignment of tracking and focus servos is complex because they are both an electrical servo loop with a mechanical component in the mix as well. And each interacts with the other. I remember a 3 day Sony course where we pulled all the theory to pieces looking at bode plots of how it all interacts. And after that told "you don't need know all that stuff though to fix them". Great
I was thinking before the analogue stages, quite how far before is hard to say though.
Hi all, back to the CD63ki. I was waiting for the laser replacement and installed it today.
The cdp spun up immediately and played better than ever. However, the audio dropped out after about 2mins and 90 seconds of play. I removed the board and checked most joints and resoldered anything that looked suspect including the regulator legs. I may have to now put the project on 'indefinite hold' until I get a scope and learn how to use it effectively.
Thanks for all your patience and suggestions. If anyone has had the same problem and can suggest a fix it would be appreciated.
The cdp spun up immediately and played better than ever. However, the audio dropped out after about 2mins and 90 seconds of play. I removed the board and checked most joints and resoldered anything that looked suspect including the regulator legs. I may have to now put the project on 'indefinite hold' until I get a scope and learn how to use it effectively.
Thanks for all your patience and suggestions. If anyone has had the same problem and can suggest a fix it would be appreciated.
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