Vox AC30 RI head with AC on the B+

[PRNDL]

I have a Vox AC30 reissue head that's fairly new. It has a GZ34 rectifier and switches between 50 (150) and 87 bias loads. There's also an effects loop with a nice bypass switch.

There's a fair amount of AC on the B+ ... it varies from about 300 to 320 volts DC (schematic says 321).
It has a fresh set of JJ tubes (the amp blew a fuse and the GZ34 tested bad) and new power supply caps, but the problem remains.

Here's a schematic
http://www.bnv-gz.de/~ooehmann/schem...e%20Manual.pdf

It occurs with the power tubes in, but B+ is steady with them out.
I tried the old power tubes, and they did the same thing, so there's something in the circuit.

Any ideas would be greatly appreciated!!

[PRNDL]

There's a footswitch for the tremolo that I don't have.

Could that cause this?

This is a cathode biased amp.

[PRNDL]

The amp sounds fantastic!

Oh yeah, I found an earlier post that talked about how the standby switch on this amp jolts the rectifier. They recommended not using it. It is between the center tap and ground.

The other thing I noticed is the tone dramatically improves when the impedance selector matches the speaker. It changes from lackluster into a mojo monster.