15 Minutes then Static... Please help!

[Trotter]

Hi All.

I'm posting this for a friend who has an older style Mesa Triple Rectifier (2-channel).

Recently the amp started getting a heavy static noise to it after about 15 minutes of playing... kinda sounded like white noise, or a TV channel with no signal (if that makes sense).

We're thinking it could be tube related and he's in the process of testing tubes, but if it's not the tubes, what else could it be? What specific steps should be taken to troubleshoot?

He took it to a Mesa certified tech who said he could not reproduce the problem and said the amp is fine... so yesterday he brought it to my house and after about 15 minutes of playing the static problem started up...

Any help is greatly appreciated.

Thank you.

[Blue Strat]

First things first, tubes.

Any of the preamp tubes could be noisy. See if any of the volume/gain controls affect the volume of the noise. This may help to pin down where the noisy tube is.