Removed the little tuner pcb to get some view room
The Power_Mute line seems to come from p38 of 100 pin Toshiba T5CC1 IC.
It is at 3.3V which seems to be for normal unmute.
Next I'll try feeding a signal directly into the edgemost chanel SBR to
confirm the amp would work if it was not killed by something in the way
of firmware or software or somesuch.