Well I think that this century has been once in the wrong hands, as the more I look into it, the more I see strange things...
May be someone tried to fix it and did not know what he was doing.(then really not) or too lazy to finish the job.
I found a missing component on a pcb. The one behing the right speaker.
By checking on the service manual the component missing is the TR30 BC337C and has something to do to power the CD when you look at the service manual at Block Diagram for power supply page 2-3.
Unless it is a b&o modification to take it out, but would be strange.
What I cannot explain is : why it worked sometimes ??? as I am not good enough to understand such an electronic datasheet.
Could someone confirm that the TR30 is the culprit and that I lost so much time trying to find the problem on a working CD mech.