ST-70 Strange Behavior

I had a nice untouched 70 show up on my bench. It has been stored a long time so needed work. I replaced the PCB board, can capacitor, bias circuit, and purchased all new tubes. Left channel is dead silent but right channel has a hum. Put a scope on it at the outputs and measured about 120 Hz so I went to checking grounds and solder joints.

I resoldered most of the joints and put a 1000 Hz sine wave on it from a signal generator. Outputs connected to speakers (with me and ear plugs). I have dummy loads but just wanted to hear if anything crackled. I started clamping on signal points inside the cabinet with my scope and noticed when I touched the case itself with my hand the hum dimmed. It didn't go away completely but definitely reduced in level. I clamped the scope onto the casing itself and I had 1.2V at fluctuating frequency but mostly around 120 Hz.

I feel like this is a grounding issue but everything is brought back to a single point on the chasis. Any thoughts?

well it doesn't sound like a tube issue per se, but you could roll some tubes through it.
I had this once with a guitar amp and it was indeed a loose pot, thus a ground issue. Your amp doesn't have any pots, but it does have jacks. I'd start on the right side jacks and go inwards perhaps. I'm not expert, but I have de-bugged a few things!