The service manuel is very helpful, we where able to restore the device to its working operation again.
Text excerpt from page 26 (click to view)
3.2.5 Signal processing section
Is the sound output from both channels (L, R)? YES Normal
No sound from either channel. YES Is 9V present at IC101 pin (8)? YES Is the audio signal (including sampling output components) output to IC521 pins ^and | during YES Is the audio signal output at IC101 pins 1 and7during playback? YES Check the muting circuit.
Compare the L-ch and R-ch to locate the defective point. YES
Check the vicinity of the Q981 audio power supply.