Thanks a lot Die_Bogener !
I now also noticed following. I touched the solder connection of the Left/Right signal wire (see red circle), with a screw driver. And immediately, the power switches ON. And when it is on, the hum/buzz gets stronger. Same happens (obviously) when I touch the back of the RCA connector (as it is the same connection of course). This does not happen when I touch the GND connection.
Concerning your advise to test by measuring (before plugging in the RCA):
- The voltage between source and 8000, both AC and DC
- Measure ground to ground
- And signal to signal
Just to be sure, do you mean …
- Ground & Signal at the RCA connector on PCB 05, at one side?
- And Ground & Signal at the P4 connector Amp PCB, as the other side?