02-15-2016, 08:05 AM
I've done a little investigating. It's the first stage of the input 12ax7 V1 & V2. I disconnected the wires from c3,c6 to the control board and all is quiet. Hooked them back up and shorted the inputs to V1, V2 and still noisy. I unhooked the sensitivity wires from the main board and it gets better but not great. I put a scope on the output of c3 and definitely see trash when the hum balance is adjusted. I'm out of time for a few days but plan to take a hard look at the cathode circuits of v1,v2 when I get back.