Thanks Doc,
I had a strange thing happen. I unmounted the c4s boards and reflowed everything. Plugged the amp back in. After about 15 minutes the right channel went out again. I poked around with a chop stick but nothing. Touched the output of the right power supply with the meter and the channel came on like always. I looked away with the probes still in the amp and slipped. The probe hit something and I had an arc flash, smoke even. Ran to both speakers but everything was still on. Even more weird, the hum I had in the right channel was gone. The amp has been playing over a day now, still all good.
Definitely not a repair method, but it worked for me.
