I finished my build last week and immediately ran into reverb hum. At first, I thought it might be because the reverb connection wires were not routed properly or sheilded. However, this turned out to be a small part of the problem. After a few days I'm thinking that either I have made a serious wiring mistake or there is a grounding issue within the PC board. Here I will add that I have checked the wiring 10X over and can find no errors. Unfortunately it seems that no one else has built this board/Princeton so there are no other finished amps to compare it to. :(
My final experiment was to remove the reverb tank return connection @ PIN 2 on V3. Doing this isolates the 'clean' side of the channel and lets you hear the entire build (preamp/tone stack/tremolo/power supply MINUS the reverb. I then reattached the PIN 2 to V3 and the hum appears. IN FACT, there seems to be some odd voltage on the chassis when the reverb return connection is made, which is odd.
I made a quick recording of the sound of the amp (playing guitar) first with the (PIN 2/V3) reverb return disconnected. The reverb tank is connected the entire time. This is using a Strat and starting off in the 'inbetween'/humbucking position and then going to the straight single coil bridge pickup for a single string 'solo', and here you can hear some typical single coil hum, but nothing odd here. Next in the (2nd half) recording, I have reconnected the reverb return (PIN 2/V3) and just listen to the amp WITHOUT a guitar plugged in. The hum should be obvious, and then, towards the end of this recorded section, I demo what happens when I touch the chassis and then remove my hand. This hum reduction (but not all of it) with the hand touch concerns me because it seems like there is a voltage present that reaches the guitar strings (when I am playing the amp with the reverb connected). Something is wrong here but I can't sort it. Hopefully someone has an idea. Oh, don't mind the playing, it's 45 degrees in my garage and I'm just making noise.