Thanks for responding to my above post. I was thinking the same things as you stated in your last post. And no doubt circuit grounds/signal grounds are more than likely connected to the chassis at various places.
Would you leave the cap where it is now located on the same AC line as the fuse? For proper operation the cap should be connected to the neutral conductor. Problem with the way it is now the neutral is fused. (I remember reading somewhere the user should reverse the 2 wire plug in the wall outlet for what sounded the best with the least, buzz/hum/noise.)
I think for a test I would first lift the cap from the chassis and then check for the proper, correct, AC polarity orientation for the primary winding of the power transformer. That will determine which lead of the primary winding should be connected to the Hot conductor and which lead of the winding should be connected to the neutral conductor. Hopefully the AC line that is fused will be the Hot. There’s 50/50 chance. I doubt back when the amps were built anybody back then checked.
At any rate if possible I would want the fuse on the Hot mains conductor and the cap connected to the mains neutral conductor to chassis ground. I would check and wire both amps the same. (Of course for many years the plug for the amps were a 2 wire non polarized plug that had a 50/50 chance of the fuse being fed from the mains Hot conductor.)
Al, what do you think?
Jim