An update.

The CD I used for testing seems to be problematic. No scratches and no issues in other players but with this particular drive/laser it causes the strange behaviour I have reported.

Shifting to other CDs (can't believe I did not try that before), I found that it works fine - except that it is now and then stuttering as if the CD is scratched when it is clearly not. Like it is having trouble tracking or something. I believe Dillen suggested in an old thread that this can be caused by a not perfectly smooth movement of the laser carriage. It might be that the gears and the rail need some extremely thorough cleaning with an even greater attention to detail than I had when I did it before. Or maybe there are other reasons behind the skipping.

In any case, I will not troubleshoot this further until I may need to use that drive or laser in another future project. I found a CDM4 based drive and PCB on eBay that swapped right into the Ouverture without any further modifications. The mechanism is a bit slower to move between tracks on the CD, sure, but it just works and I have the same type in my Beocenter 9500, which I like the sound of very much.

So, although I have not found what caused the initial problem, I consider the case closed, for now.

Thanks a lot for the feedback provided. It warms my heart when you fellow forum dwellers selflessly lend me a bit of your time. I will try to do the same in return. :-)

Hi Martin,

thank you very much for your update! So many other posters tend to "forget" to post a final message telling the readers and those members who tried to help whether they were successful or abandoned their repair attempt, which leaves every future reader guessing. 🙁

Since you have a used CDM4 mechanism now, did you recap the servo board first or do you leave this for a future date? Did you measure and readjust the laser current as per service manual? (You should at least check!)
Since you say "The CD I used for testing seems to be problematic", is it right to assume that you have skipping problems with the CDM4 on this disc too?

I have some more info on the CDM12 mechanism too, but I'll have to leave that for later.

Hi Manfy,

No, I did not recap the servo board (yet) since it currently works. I know it is just a matter of time but I have not investigated yet which would need a replacement. There is no "kit" available that I know of like there is for the Beocenter 9500 drive for example. Not sure it it is the same ones on that one?

I have not made any measurements or adjustments for the laser current since it it used with its original servo board. Is this needed regardless of that?

There is no skipping problem with that CD on any other drives that I have tested. Only this CDM12 one.

Martin wrote:

There is no skipping problem with that CD on any other drives that I have tested. Only this CDM12 one.

Good! That proves 2 things:
1) It's not the CD that was seriously flawed but a problem with the CDM12 mechanism
2) Your new used CDM4 replacement drive is in a reasonably good condition

Regarding recapping and laser current adjustment:
-) it's fine to test the drive as is first, considering that the seller claimed that it was working fine. I would have done the same.

-) laser current adjustment: Every B&O manual I read in the past recommends checking this setting whenever you change the laser or the servo.
You don't know the operating condition of this drive in the donor unit or whether the laser current has been adjusted before, so checking this value is certainly recommended -- if for no other reason than having a reference value for that time in the future when the laser starts to fail and when you need to start measuring and take action.
Remember: you don't know how often this drive was used. From the CDM12 Industrial drive I remember that it was speced by Philips with a lifetime of 7500hrs. The non-Industrial versions were speced with 5000hrs. Some point down the road the laser diode will deteriorate to a level where it is not reasonably functional any more.
The service manual shows that you should read 50mV +/-2mV across R16 on servo board 8 when you're playing a known good CD. If that value drops below 25mV it is a sign that you will start seeing reading and tracking problems (be it because of cap issue, laser deterioration, lens contamination or whatever).
So yes, if your unit is still open then measure the laser current and record it. [** CAUTION: pls see footnote]

-) recapping: If everything works fine and the laser current setting is close to 50mV at R16, there is no need to recap.
However, I would do following: take several clear pictures of the board. Record all e-caps and their values. If you have a reliable multimeter with C-measuremnt, measure their values and write them down. If you have an ESR meter, do the same. Now you have a status quo that you can use if and when you run into problems in future.
I would also measure the sizes and pitches of those components, so that you can order replacement parts whenever needed (and without having to tear the unit apart first).

BTW: The ominous capacitor that is causing all the fuzz is C100 with 47uF on PCB8 . If you ever have to change it, it would make sense to change the other e-caps too since all of them are 20+ years old and they will deteriorate sooner or later.

Here is one thread on the issue, which might interest you: <

Many thanks for your insights on the topic.

Since the system is put back together, polished up and found its place on a kitchen sideboard already, I don't believe I will do any measurements right now. I believe the drive and the board was used together before, which would lessen the need for any adjustments.

But I will return to this post if the need arises - if any problems with the "new" drive would occur! Again, thanks a million for the good advice so far!

Sure thing!
Just take it as a "best practice procedure" for your next project. Measuring and recording takes little time while you have the board on your bench, but it can save you from a lot of guesswork and troubleshooting the next time around.

Cheers!