Triple Rec Red Channel Volume Drop - Tubes?

[Freefall]

Recently I acquired a used 2 channel triple rec. The tubes are original stock Mesas, unknown age, so they might be quite old.

When I switch to the red channel, the volume starts off normally but within a few seconds it drops to about half of normal and there's a loss of high end. Orange channel is fine. I'm using Bold and Silicon Diodes. Does this sound like a tube issue? If so, pre- or power? If it's preamp, any guidance as to which one(s) would only affect the red channel?

One other rookie question... if I'm going to have to try swapping in and out the preamp tubes, is it easier to take the amp chassis out of the headshell so I don't have to pull the power tubes out of the way each time?

Thanks in advance for any help!

 

[mefgames]

I had the same problem with my TremOverb. Took it to Mesa, and they replaced some LDR's. (Light Dependent Resistors) Could be the tubes though. I'd start there.

mike

 

[Freefall]

Little more info... I realized that I had the red channel setup in vintage mode so it sounds like the orange channel. The actual problem is that when I switch to the red channel, it starts out in modern mode, and then drops into vintage after maybe five to ten seconds, which (I believe) is quite a bit quieter and with less high end than modern mode. So I guess the switching is the actual issue.