The last days I repaired another CDM2 from a CD150 donor. The issue of the device can be described as a kind of “cramp”. The swing arm moved to the top position and stopped there as well as the focus got stuck in the upper position and both do not react.
A working CD150 decoder unit helps to test the CDM2 and to get easy access to it. The CD555 would be much too complex for this task.
First thing, as always, is to replace all the capacitors and put the ICs on a socket. After checking the voltages of the ICs I tried to replace them to see if the problem still exists or if one got toasted. Well, this might not be a professional way – it reflects more or less the hope that it will be an easy fix. Anyway, replacing the uProc and the motor driver has not changed the behaviour.
However, the issue with the swing arm guided me directly to the outputs for the radial motor (31-11 & 31-12). After some measurements of the components, the transistor 6109 has show some unusual behaviour. Replacing the BC858 with a BC858-40 has done the job and the CDM2 is now fully working.
Afterwards I tested another CDM2. Unfortunately it does not read the TOC, everything else seemed fine. I checked the controller and it is working, the swing arm is moving and also reacting in the demo-mode as expected. From time to time the CDM2 reads the TOC – which drove me a little bit crazy. Finally, I figured out the thin metal plate of the focus is broken. After some tests it broke completely and become useless. Now, the interesting question is… where to find a spare part or how to replace it?
