Hello, my experience was unfortunately, that this is a beginning of the end of a a beolab 4000 speaker due to the foam-rot issue, just search the archive forums for „Beolab 4000“ and „foam“. These damping materials inside the Beolab 4000s are getting old and sticky and etch the PCBs to death. Resulting in the case that Beo4000’s do not switch on any more.
BTW, did anybody manage to repair them?
Best regards