Amp was purchased off eBay as a repair/resell item. Amp listing claimed untested, unknown operation.
I first check B+ and GRD with an ohm-meter to confirm no shorted PS FETs, that checked OK. I applied B+, GRD and +12REM and the amp turned on and produced an audio output, channels 1, 3 and 4, no output on channel 2. I found a burnt capacitor that supplies VCC to channel 2 PWM circuit.
I replaced the capacitor with a Multilayer Ceramic Capacitor SMD 1206 0.1uF 50volts.