Mesa Mark V 35 Combo Noise problem

[Niki512]

Hi Mesa-Community, since yesterday, my Mark V 35 Combo makes the following noise:
https://soundcloud.com/niki512/mesa

It appears when no guitar is plugged in, but it get's louder when I connect a guitar to the amp and start to turn up the guitars volume poti. The noise is way louder on the lead channel than on the clean channel, I've already changed cables, the guitar, I even tried the amp in another house just to get sure theres no problem with the electric socket. The amp hasn't been moved either. I've also tried touching the tubes carefully, that doesn't take any influence. The noise is always there...

I'll bring the amp to a nearby music store the next days, but I was wondering if anybody in here has a suspicion where the noise may come from...
Kind regards,
Niki

 

[jb's 52]

My experience with the bigger Mark V but it sounds like it's time to roll pre-amp tubes.
I had a very similar sound and it turned out to be one of the pre-amp tubes.

Grab a good pre-amp tube, replace V1, if the sound is still there, pull and try in V2...repeat as needed.

If you can, get 3 or 4 known good ones and replace, say, V1 - V3. If the sound goes away, put back the old ones one at a time to find the culprit. Cuts the troubleshooting time in half...hehe.

Always good to have a 1 good pre-amp spare, 2 good power tube spares, and 1 good rectifier tube spare imo.

Good luck!!