D-555 focus/tracking dropping out

d555cd

Hello all, this is my first time working with a CD player, though I do a lot of microelectronic design professionally and some SMD rework as needed on other types of systems. I'm by no means a rework specialist, though, and I know next to nothing about CD players in specific.
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I have a D-555 here that originally had the stuck sled issue (which I fixed). It played a bunch of discs ok, but some discs it wouldn't accept at all - it never got past trying to get a good read of the TOC, and aborted (it wasn't the "no disc" scan, it was something a bit more intensive than that). It struggled a lot on track 1, though, so I ran through the service manual's tracking and focus gain adjustments (but I didn't mess with anything else as I didn't have a "CD Jig" whatever that is). +6V and +3.4V on the main board measure within spec using the AC adapter. That improved it for some discs quite a bit, but others it still refused to read, even brand new ones.

After a while, I noticed that it would also not play two discs back to back - if I successfully played one disc, it would definitely not read the TOC of the next disc without being physically unplugged and then plugged back in after some time had passed, even if the second disc was one it had just read without an issue (or was really just a re-play of the first disc - no disc insertion was necessary to trigger this condition).

This got worse, and so I decided to put it back on the bench and see if maybe some of the adjustments were out again or if I'd messed something up or, who knows, just look at the internal signals again and see if anything's obviously amiss.

Lo and behold the focus coil and tracking coils aren't activating (randomly, but now more often that not they don't activate even during the disk scan), and the internal signals for FE and TE are also silent in those cases, or mostly silent with the occasional glitch. When I put the unit in test mode and try to do a Tracking Balance adjustment, for example, that signal is just a flat line in these cases.

I was able to get the unit to spin up and lock on to the disc a few times on the bench, get a solid tracking signal (Note 1), and then try to move on to getting a proper eye diagram on the RF as if I were doing a focus bias adjustment. At the point that I press the Key-Mode button to tell the unit to start tracking and activate the sled, though, the unit "jerks" back to the inner limit, the focus and tracking signals go entirely off, and the disc spins up to maximum speed. Nothing seems to get it out of this mode except pulling the power.  Last time I had the unit in test mode, this wasn't an issue and it never needed to go re-read the TOC or the inner track data it just started to play from where the sled was - which I think is what this particular test mode is supposed to do, from the description in the service manual and from what it did the first time everything seemed to just work more or less ok.

Any ideas on what to check? I'd be grateful to get this unit back into working order.

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Note 1: The tracking signal was never a perfect sine wave, it was always a bit of sine-like signal with some weird longer asymmetric sine-like signals every so often in it, I have no idea if this is normal).  



Note 2: I checked the laser power consumption across the precision resistor and it's exactly spot on the label (KSS-222A, 29.6mA expected current labelled).

d555cd

Well it turns out that the ribbon cable to the focus motor is badly cracked right at the PCB-end connector. I don't know what *else* is broken, but at least that is.

d555cd

Ok, so the ribbon cable is replaced, and the RF "focus bias" has been adjusted, and the set generally plays ok, but it still has other issues. I'll open a new thread for them.

kaosun

Try adding one drop of lubrication oil to the upper bearing of the spindle motor will help a little bit. If it's possible, replace the laser KSS220 for a try. Play a commercial disc, adjust your TB,FB to get best RF pattern at amplitude of 1.2Vp-p. Ignore the current on the label, when you get 1.2Vp-p, if you measure the laser current again, it will be greater then the labelled value, this called "aging".

d555cd

Hi Kaosun, thanks for the reply! I will try your advice. I have a few questions to be sure I understand correctly:

1. What exact type of lubrication oil should I use for this? Do I simply apply it to the point where the spindle shaft sticks out from the motor? Or do I need to disassemble the motor somehow?

2. When you say TB, FB you mean specifically RV502/RV503 to adjust the bias? I want to be sure, because I did those adjustments and only got max 0.9Vp-p on the RF at the cleanest, and I want to make sure you don't mean for me to adjust the gains, RV501/RV505.

3. I noticed that the FE signal was 250mVp-p, which is significantly more than the 50mVp-p the service manual recommends. Is this normal, or should I adjust it somehow?

4. Where can I buy a known excellent condition KSS-220A for this model without paying a small fortune?

Thank you!