Yes. I've replaced them in the meantime. Apologies for the confusion. I took a photo only from the state before replacement. I'll upload one from the state after when I open the bottom lid next time.
looks lovely. In my experience, I associate the use of my scope and your advice with success 🙂 My son gave me a used Fluke which should be much better than the one I used before (or rather did not really use... and anyway it should also be good enough). I now need to find the point where to hook the probe to.
There is also a resistor on the servo board (3240) across which the voltage needs to be measured in order to see if the focus is ok (+- 100mV). The focus height apparently is set with the allen screw inside the motor axis.
Philips set up procedures were always obscure and convoluted 🙂
Focus adjustments will always show in the RF signal. Better focus = clearer and better defined 'diamond' shape in the centre of the waveform and maximum amplitude.
Laser power adjustment the Philips way was also bizarre by looking at the volt drop across a resistor that monitors the total photo diode array current. Easy way, just look at the amplitude of the RF.
Focus adjustments will always show in the RF signal. Better focus = clearer and better defined 'diamond' shape in the centre of the waveform and maximum amplitude.
Laser power adjustment the Philips way was also bizarre by looking at the volt drop across a resistor that monitors the total photo diode array current. Easy way, just look at the amplitude of the RF.
Ok. Looking at the Philips manual how to do it is frightening indeed ... and even the workarounds suggested in German forums are daunting.
So I'll become even more friends with the scope. Cross your fingers, please!
So I'll become even more friends with the scope. Cross your fingers, please!
Philips procedures were always strange. Some manuals called for a plain glass disc for adjustments as I recall, I mean who has one of those lying around.
You've probably already seen this but it does have some good scope shots in it showing the RF:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
Use any good quality commercial disc but never a CDR. The RF will look the same for any disc.
You've probably already seen this but it does have some good scope shots in it showing the RF:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
Use any good quality commercial disc but never a CDR. The RF will look the same for any disc.
Yes, I have seen your restoration story and loved the sound and logical way you proceed. Will read it again. I also have a SONY with a KSS mechanism that is acting up (I put that back into the stash a year ago, having lost too much time with it... but maybe I'll learn).
The successful restoration threads of CDM0/1 reading problems on German forums often involve using (and first making, as "who has that lying around", as you say) that transparent disc. I have the Philips test sample discs, but a transparent one is not among them.
The successful restoration threads of CDM0/1 reading problems on German forums often involve using (and first making, as "who has that lying around", as you say) that transparent disc. I have the Philips test sample discs, but a transparent one is not among them.
I finally found some time to hook the CD204 to the scope. Pic see below.
The eye pattern is not razor sharp (compare with the black lines of the scale on the screen). The voltage (1.2V; set to 0.5 V/Div.) seems a bit too high, according to the SM should be 1V. But possibly still within the margin.
The RF pattern oscillates slightly. It is not just a fixed image but slighty wobbles rhythmically. I made a video of this and also of the motor movement (available here: https://www.dropbox.com/s/xtmseffivm0ykxy/RF pattern_movement.MOV?dl=0 and https://www.dropbox.com/s/rfghpacyzgpnt5x/radial motor movement.MOV?dl=0).
I refrain from turning any pots so far. Any ideas? Philips writes that if the image is not stable, the motor might need service.
Some recommend re-lubricating the motor shaft.
While I have been typing this post I have been listening to the player (through headphones) and it did not skip once. Went without fault for at least three or four titles on the CD. It skipped once or twice when I started the CD in the machine with cover and bottom removed. When this happened, the laser started to "twitter" first for two or three seconds and then made a skip.
I have observed that the lower fringes of the flexprints for the laser assembly are very close to the bottom plate.
The eye pattern is not razor sharp (compare with the black lines of the scale on the screen). The voltage (1.2V; set to 0.5 V/Div.) seems a bit too high, according to the SM should be 1V. But possibly still within the margin.
The RF pattern oscillates slightly. It is not just a fixed image but slighty wobbles rhythmically. I made a video of this and also of the motor movement (available here: https://www.dropbox.com/s/xtmseffivm0ykxy/RF pattern_movement.MOV?dl=0 and https://www.dropbox.com/s/rfghpacyzgpnt5x/radial motor movement.MOV?dl=0).
I refrain from turning any pots so far. Any ideas? Philips writes that if the image is not stable, the motor might need service.
Some recommend re-lubricating the motor shaft.
While I have been typing this post I have been listening to the player (through headphones) and it did not skip once. Went without fault for at least three or four titles on the CD. It skipped once or twice when I started the CD in the machine with cover and bottom removed. When this happened, the laser started to "twitter" first for two or three seconds and then made a skip.
I have observed that the lower fringes of the flexprints for the laser assembly are very close to the bottom plate.
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Interesting. The radial motor wobble (and so the RF fluctuating) looks almost as though the disc may not be running true in the horizontal plane. To see such visible wobble suggests the laser is actually following the track on the disc (or else it would loose lock). Very odd but its an area worth looking at.
Has the platter any movement to it in the horizontal plane? and if you rotate the disc slowly by hand can you detect any eccentricity?
Has the platter any movement to it in the horizontal plane? and if you rotate the disc slowly by hand can you detect any eccentricity?
Thanks, Mooly, for getting back! I'll check that now and report back. Unfortunately, the CD sits beneath a "cage" in case of these early Philips mechanisms, not easily accessible. But I can look from below.
I know that the plastic puck that goes down on top of the CD wobbled visibly when I looked last time, quite a bit actually.
I know that the plastic puck that goes down on top of the CD wobbled visibly when I looked last time, quite a bit actually.
The CD does not wobble much. See video (https://www.dropbox.com/s/ucd3mxwpxhsqm9s/CD204_disc_spinning.MOV?dl=0).
The clamp though seems to move in a slightly de-centred way. I removed it in order to look a the white grease around the ball bearing which seems dried up. I have not yet understood how to get the puck out of the holder and will not force it – but maybe clean out the dried grease with a paper and relube with some new (I think I have this white grease lying around somewhere which came with some SONY replacement parts. See pic.
I remember having read that friction of the puck in its bearing might cause skipping in Philips players – but I don't remember where and it might have been anecdotal. Anyway, fresh grease might not be a bad thing.
The clamp though seems to move in a slightly de-centred way. I removed it in order to look a the white grease around the ball bearing which seems dried up. I have not yet understood how to get the puck out of the holder and will not force it – but maybe clean out the dried grease with a paper and relube with some new (I think I have this white grease lying around somewhere which came with some SONY replacement parts. See pic.
I remember having read that friction of the puck in its bearing might cause skipping in Philips players – but I don't remember where and it might have been anecdotal. Anyway, fresh grease might not be a bad thing.
PS I also observed that after reading the TOC the disc continues spinning. It will only stop when hitting "stop". Not sure if this is normal for a CD204, nor if this was the case before, when the player did not skip yet. It might be the link to a fault.
Does the unit skip more in the beginning of the disk and when trying to seek a track? Its worth looking at the spindle motor voltage gain. If the motor is getting weak from having bad brushes, it will skip more in the beginning of the disk where more rpms are required of rhe motor as well as reading toc.
The unit hanging after reading toc is a symptom of a weak spindle motor. You'll also want to check the drive voltage for noise from a bad drive transistor or from the servo output to the base of the drive transistor.
That's normal on a lot of players for the clamp to wobble. It is whether the disc edge wobbles in a similar way that is what you do not want. That would imply the disc is not centred correctly or the motor/platter itself is not running true.
The earlier video showing the pickup wobbling to and fro is because the laser is attempting to follow the track on the CD which I think must also be wobbling. There look to be quite a lot of movement tbh.
I'm sure you've tried more than one disc as well 🙂
Yes, checked with more than one CD.
Before the player skips, it does this "laser chirp" for three seconds. The eye pattern during this continuously compresses in amplitude (until it is slightly below 1V). Then the skip occurs, jumping ahead by about 2-5 seconds. Amplitude jumps back to about 1.2V.
This is most prominent after starting the disk, in track 1, doing it every ten seconds or so in the beginning. if I go forward track by track the titles are found without problem, but skipping is also there in later tracks. It becomes rarer when the player is left playing but re-occurs randomly even then.
Before the player skips, it does this "laser chirp" for three seconds. The eye pattern during this continuously compresses in amplitude (until it is slightly below 1V). Then the skip occurs, jumping ahead by about 2-5 seconds. Amplitude jumps back to about 1.2V.
This is most prominent after starting the disk, in track 1, doing it every ten seconds or so in the beginning. if I go forward track by track the titles are found without problem, but skipping is also there in later tracks. It becomes rarer when the player is left playing but re-occurs randomly even then.
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It does not hang, the player is responsive, TOC is displayed, I can press play any time, search titles etc., only that in this idle phase the disc is spun continuously. Checking drive transistors – transistors on the CDM0 PCB especially – will be considered, thanks! Any particular suspects?
I have repaired skipping CD players a few times. I associated the problem more with an aging laser assembly. The CDM0 is very old now correct? From my reading they do loose power over time. Would be interested in feedback. After replacing lasers in almost all units it has solved the problem. That was after a could cleaning of lens and slide rails before changing of course.
Do you get the same symptom of reducing RF level if you physically try and (gently) stop the arm moving?
Loss of emission from the laser is normally something you would see in the RF (low amplitude). That sort of deterioration is usually a constant, not intermitent.
Some pickup issues often relate to the lens suspension.