Well that seems all to point back to 6118 (circled in your images) which I just tested ok but that does not mean that it is not failing intermittently. Thanks!
With that knowledge I might just swap it – BC549 is what I think will work, agreed?
With that knowledge I might just swap it – BC549 is what I think will work, agreed?
Sounds like worn spindle motor bearings to me. Some lube may help but a new motor is the best fix, if available.
I maintained hundreds of CD-R/DVD-R drives that ran 24/7 at my last job in the disc replication industry.
Most common failures were the spindle motors and laser assemblies.
I maintained hundreds of CD-R/DVD-R drives that ran 24/7 at my last job in the disc replication industry.
Most common failures were the spindle motors and laser assemblies.
I suspected 6118 was going to measure correct once out of curcuit.
Spindle motors are wear items on these players and usually the brushes are first to go. The TOC won't read to start with if this is the case as the CD will spin fastest at TOC read and progressively slower towards playing the end of the CD. The drive voltage from the servo will be higher, indicating a lack of motor torque.
The spikes mentioned in the error correct waveform are a giveaway of something noise after the control chip conmanded output (not accounted for in the feedback signal). This indicates a noisy component after the drive signal comes from the control circuit. When the player is paused, the tracking error amp signal is ignored and the radial motor servo will just repeat the voltage waveform window its given to read that frame of the CD until unpausing the player.
The only other thing to check IMO is power supply noise on the control IC and servo block, specifically the error op amp. I dont see the schematic section for this in what is posted here, only the looped connection to the radial arm motor.
Just to refresh my memory here, does the player skip forwards or backwards when playing? If not, does it skip ahead or back in the track by alot or a little? Is the player overly sensitive to vibration?
A sub for the BC548B isn't critical. Almost any common To92 will work in a pinch. I dont think 6118.is suspect from what I'm getting here. The source of those spikes are what you're looking for and tracing the waveform back from the radial arm drive signal is what you're needing to do. Have you gotten any pictures of the spikes in the control signal? How high are they incomparison to the overall amplitude of the waveform?
Spindle motors are wear items on these players and usually the brushes are first to go. The TOC won't read to start with if this is the case as the CD will spin fastest at TOC read and progressively slower towards playing the end of the CD. The drive voltage from the servo will be higher, indicating a lack of motor torque.
The spikes mentioned in the error correct waveform are a giveaway of something noise after the control chip conmanded output (not accounted for in the feedback signal). This indicates a noisy component after the drive signal comes from the control circuit. When the player is paused, the tracking error amp signal is ignored and the radial motor servo will just repeat the voltage waveform window its given to read that frame of the CD until unpausing the player.
The only other thing to check IMO is power supply noise on the control IC and servo block, specifically the error op amp. I dont see the schematic section for this in what is posted here, only the looped connection to the radial arm motor.
Just to refresh my memory here, does the player skip forwards or backwards when playing? If not, does it skip ahead or back in the track by alot or a little? Is the player overly sensitive to vibration?
A sub for the BC548B isn't critical. Almost any common To92 will work in a pinch. I dont think 6118.is suspect from what I'm getting here. The source of those spikes are what you're looking for and tracing the waveform back from the radial arm drive signal is what you're needing to do. Have you gotten any pictures of the spikes in the control signal? How high are they incomparison to the overall amplitude of the waveform?
The BD635 and BD226 are rated at 3A and 1.5A respectively which seems a bit excessive. I think the BC549 is a bit tight at 100ma though.
I would have thought a BD131 or BD139, in fact I can't see it being very critical at all tbh, just something a bit higher rated than BC549 🙂
And beware the pinouts, check check and check again before fitting anything.
If you want a simple way to remotely heat 6118 to check it for temp based failure, you can attach a flame proof 100R 1/4 W resistor with RTV and heat it by running wires out to a 5V USB supply.
6118 is very important to the safety of the laser. I think I would be inclined to swap it rather than poke and prod it with heat. Just make sure you get the pinouts correct as would think the BD's will be of the standard ECB (looking left to right from the front) and the BC you mentioned is CBE. There is no room for error on this one.
Sorry, I confused 6118 with one of the other servo output transistors. Yes, that would be stupid to provoke the laser current drive. I dont think it has anything to do with the problem he's having with the player anyways.
It skips only forward, by 5-6 secs, and more on the first and last tracks. No particular sensitivity to vibration.
Hmmm, I tend to agree. It's just I have definitely replaced those in the past for some weird issue but it was 3.5 decades ago now 😱 Also of course the electrolytic cap on the base of that transistor but those have been changed now anyway.
I've a feeling the problem showed when scoping the emitter voltage of the transistor. I think it was 'noisy', the actual laser current that is, but you need to be so careful doing any tests around that area that I'm not sure I would recommend trying to measure.
This indicates non linear behavior from the radial arm and points towards a drive error after the control IC output. IOW something in the drive servo is injecting voltage and noise glitches, commanding the sporadic movement. You'll have to trace pins 5 and 8 of the A11 ribbon cable back to the main PCB and see where the noise is being added. Could be power supply related or any component in between from the control IC forward (not discounting the IC itself). If you could post the mech control block circuit, that would help.
Attachments
The manual i found online is incomplete. Its missing the main u-con schematic. You won't be able to trace the circuit without it unless you're knowledgeable about typical older philips CD player layout.
What is the PN for the laser assembly. Is it a KSS...
Check with Liberty Electronics online. They sell lasers and other CD parts
Check with Liberty Electronics online. They sell lasers and other CD parts
Laser has 99.9% nothing to do with the issue. The RF from the pickup is stable, so that's a solid indicator there's no issue with the laser.
Thanks so much guys for the great input! Was deeply immersed elsewhere today and will follow up later. Sounds like a promising track to trace back!
The service manual for the various CDM-0 drives is here in my dropbox: https://www.dropbox.com/s/xm4frfnedk4hi5r/philips_cdm0_cd_mechanism_sm.pdf?dl=0
My version (VI) starts at page 15.
The service manual for the CD-204 is here: https://www.dropbox.com/s/2qas08j390iiv2j/philips_cd204_service_de.pdf?dl=0
My version (VI) starts at page 15.
The service manual for the CD-204 is here: https://www.dropbox.com/s/2qas08j390iiv2j/philips_cd204_service_de.pdf?dl=0
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Tracing pin 5 an 8 from the A13 connector on the motor board in the servo board schematics.
The radial motor + (pin 5) goes here on the servo PCB:
The focus motor + (pin 8) goes here below
(circled in red is the cap that was an orange tantalum as I remember and wich I first forgot to swap in 2020. It caused skipping then, actually. I replaced it some days later after I discovered it with a 1uF film, which after looking at the schematic I again swapped with a 100nF film two days ago, hoping that would lead somewhere. I think there must have been something bigger than 100nF in 2020. But all this might not lead on the right track..):
While testing some transistors today I found that 6231 tested only "diode" in circuit (pin 1 not connected). Its complement, 6231, tested as two diodes. I pulled 6231, but out of circuit it measured ok, so I put it back. Can this be a track?
the +1 rail is involved in the RM+ and FM+ processing.
The radial motor + (pin 5) goes here on the servo PCB:
The focus motor + (pin 8) goes here below
(circled in red is the cap that was an orange tantalum as I remember and wich I first forgot to swap in 2020. It caused skipping then, actually. I replaced it some days later after I discovered it with a 1uF film, which after looking at the schematic I again swapped with a 100nF film two days ago, hoping that would lead somewhere. I think there must have been something bigger than 100nF in 2020. But all this might not lead on the right track..):
While testing some transistors today I found that 6231 tested only "diode" in circuit (pin 1 not connected). Its complement, 6231, tested as two diodes. I pulled 6231, but out of circuit it measured ok, so I put it back. Can this be a track?
the +1 rail is involved in the RM+ and FM+ processing.
Ah, and btw, the headphone circuit stopped working in the last days while I was listening for skipping while I had the machine on the bench through headphones. It first started distorting, then went dead. It is now disconnected. Also +1 / -1 rail. The player skips also with the headphone amp disconnected.
I'd monitor pin 2 and 3 on 6211 and compare with op amp output to servo amp. 4053 ICs are known to have weird issues. The cmos type device can behave intermittent in very strange ways. The way its being utilized in this circuit makes it susceptible to supply noise. Keep an eye on the drive waveform to the radial motor and try to catch the behavior when it skips. If it jumps when the player skips, then its being commanded to do so by the servo input, which means you have to find out if there's a power supply noise issue or the clock oscillator to the u-con is cutting out or drifting. You have to be patient here with this issue. I still believe the issue has to do with a servo input error induced by intermittent noise. These old CDPs are sensitive to power supply issues, so its wise to monitor the supply rails first to see if there's any weirdness and rule it out.