Philips CDM12 no disk recognition

Hartmut, it has been a while since I did this repair : There are two boards inside the unit, one main board and one board at the rear with the D/A converter. On this board is a circuit generating a clock signal which is needed for the CD drive unit. I had a bad connection between this circuit and the CD drive board. I believe it was the connector between the two boards. Sorry, I did not keep photos.
Hope that helps.
 
Best is to use a scope and follow the signal path from the D/A board to the CD board. Good Luck! Also: As far as I remember power to the D/A board is supplied from the Main Board. There are a number of 5V ICs next to the transformer. Check voltages from there to the D/A board as well.
 
I use the ML39 also as a D/A converter for streaming. From this side everything is working as it should. CD‘s were playing also. Until now. It is the same behaviour as you described. I‘ll have a look at it. ML-service station in Germany is not very good.