Help needed with Marantz cd63ki not recognising discs

[mercedesjenz]

Heelp! I am the most dangerous of creatures: someone who knows a little bit about something but not enough to get out of trouble. Besides I am brand new here...

The problem: I bought a Marantz CD63Mk2 KI off ebay as "untested" (i.e. broken) in the hope, that it would be easily fixable. I already have a basic CD63 which i got off the car boot sale for a fiver and which i got to work by lubricating the motor, so i thought how hard can it be?

Here's what I have done so far, to no avail:
Swapped the two drives over: The KI's drive does not work in either, the normal 63's drive works only in the 63.

Got the service manual for the 63 (have not been able to find one for the KI) and went through the self-test procedure. Both drives apear to be doing what they should and there are no error messages, so does that mean there is something wrong with the clock mechanism on the KI?

Then again, both the drives are the CDM12, therefore identical and both of them work fine in the test, so why doesn't the KI's drive work in the normal 63?

I hope there's someone out there who's got some ideas.
Please help...

[L700]

i think KI using CDM 12.3