AC30 CC2 volume probs

[LarBal]

This amp came in a couple months ago for new MM Output Transformer, and customer provided ALL new tubes. He loves it, until about 3 weeks after the repairs, all volume disappeared.
I've looked it over, and checked all tubes, voltages, etc, even swapped the old working OT back in, to no avail.
I don't have a scope but am tracing the signal w my meter and an Iphone sig generator app.
I'm looking at the crossline MV. i believe that's what it's called. Ken Fisher called it type 3 I believe. It's essentially a pot wired as a rheostat between the output of the PI, after the coupling caps, correct? (or at least after the 10K resistors, who's purpose I'm unsure of honestly).

Anyways, I get faint signal through the speaker when the MV pot is on 1-9, and there is no level change. On 0, there is nothing coming out of the speaker.
At the junction of the 10ks and couplers, I get about 5VAC of signal. on the other side of the couplers, that touch the MV pot, I get 300mV, no matter what the knob is turned to.
I'm also getting continuity between all pins of the 500K MV pot.

Is this pot bunk? I figured I would ask if there were any other possibilities before I start pulling that board
Vox_ac30cc2_ac30cc2x_2005_sm.pdf

[Helmholtz]

Disconnect the MV pot and see if this restores the volume.

[x-pro]

"At the junction of the 10ks and couplers, I get about 5VAC of signal. on the other side of the couplers, that touch the MV pot, I get 300mV"

On the right side of R31 and R32 is 5 VAC, and on the left side of R31 and R32 is 0.3 VAC?

[LarBal]

"At the junction of the 10ks and couplers, I get about 5VAC of signal. on the other side of the couplers, that touch the MV pot, I get 300mV"

On the right side of R31 and R32 is 5 VAC, and on the left side of R31 and R32 is 0.3 VAC?

The other way around, 5VAC at the junction of C20 and R31, .3VAC at R31 and the pot, same with other side of PI

[x-pro]

I could be wrong, there may be a short circuit of the first grid to the cathode of one of the output tubes.

[LarBal]

I got it working, I'm just not exactly sure what the problem was. That pot isn't easily removed, so I just removed as much solder from the pcb pad as possible, in an effort to at least wiggle the legs back and forth.
I thought that worked , but not only did the sound come back in full, but the MV functions properly. Cold solder joint? I resoldered everytjhing and it all works

[Helmholtz]

Cold solder joint? I resoldered everytjhing and it all works

A bad solder connection would not explain the symptoms.
There must have been something shorting pot pins.

[LarBal]

A bad solder connection would not explain the symptoms.
There must have been something shorting pot pins.

Yea exactly, a bad joint would have allowed ALL signal through, I imagine.

[Chuck H]

Ok, but what could have been shorting the pot? Surely there wasn't so much solder on the pads as to bridge. So I'm shinking dodgy pot. And the work you did (heat, aggitation, etc.) somehow got it working. For now anyway. I'd clean the pot by blowing it out (not pot cleaner) and retest. If it's still working I would tell the owner that the pot is working fine now, but it's still suspect.