Just to confirm, I remove P5 connector completely, inject 4.6V to pin 3/4 of P5, then monitor the voltage across R95 with a multi-meter (service manual says to use an oscilloscope).
One thing i’m unclear about is the ground situation. If I understand correctly, removing P5 also removes the chassis ground wires from microprocessor board 2. I would need to connect power supply ground to a ground point on board #2, and not the chassis ground point up by the amplifier board.
Thanks again, Glitch.