1969 Fender Twin rewired

[C Moore]

OK -
I replaced the board, components, pots, jacks, etc. Basically the only things original are the three transformers, choke, and tube sockets.
On channel 2 there is what sounds like ground hum when the volume knob gets up past 2:00-3:00. It comes on real fast. Does not matter if there is a guitar plugged in or not. Channel 1 is fine. I have changed tubes, used shielded cable from the volume pot and the main input (ground only on the pot and jack side of the cable), played with lead dress for 15 minutes. Nothing in the lead dress makes ANY difference to the noise. If I pull V2 the noise/hum goes away. Can a new pot have a noisy spot like that?
Anyway.... do you guys have any thoughts or suggestions?
Thank You

[PaisleyTube]

I guess: check the grounding

(did you use the original groundingpoints at the brass plate behind the frontside of the chassis?)

[Structo]

Also, what did you do about the heater circuit?

Does the PT have a center tap for the heater wind?

If not, did you create a virtual center tap by using two 100 ohm resistors, one from each wire to ground?

[C Moore]

The pots and cathodes are all grounded via the brass plate at the front panel. That is to say, I just reused the ground scheme that Fender had set up.
There was no CT for the PT so I replaced the existing 100 ohm resistors with 100 ohm, 1 watt, carbon film.
I will be the first to admit, I do not know anything regarding the theory of ground. All I know is that it is important, but I have no idea what constitutes a good ground system.
So it kind of seems weird that the only thing making noise is Channel 2 when the volume knob gets past 2:00.
Thanks
These power tubes are RCA and look very old (maybe they are original. i do not know). Is it possible for power tubes to be noisy at high volume? I suppose they would hum on both channels though, not just channel 2.