Mark V25 intermittent static

[Phil the Kill Bill V2 guy]

I bought a Mark V25 head new in 2013 and have used it on hundreds of gigs. I love it, it's my favorite amp.
Recently on 3-4 gigs, it developed an intermittent static that sounds like when you're trying to find a radio station but you're nowhere near it on the dial. It has happened in 3 different venues
It happens even when there's no guitar or pedals plugged in. One time as soon as I took the amp off standby the static started, but subsided halfway thru the set. Another time the amp performed perfectly for the first set, but the static started up later on the second. The amp did not lose power or volume. I got around the static somewhat by turning up the clean channel volume and turning down the master so the guitar sound was somewhat masking the static noise.
Any ideas on what the problem might be ?
I'm tempted to bring it to an authorized Mesa repair shop, but since the problem is intermittent I'm worried they'd call and tell me nothing's wrong with the amp.

 

[bandit2013]

Sounds like power tubes are just not happy. I had a good new set of power tubes to try out in my JP2C, nothing but static. The original power tubes I had in it developed a static noise off and on, sometimes I would never hear it, then it would become an issue and that is all I would get. That can happen with new tubes (actually they were the STR440 tubes that were new in the MWDR). No issue with the old or new tubes in the MWDR, just not the JP2C. Almost thought I had an issue with the amp. Got another set of power tubes that were not the STR440 (out of production) and have not heard any noise at all except for what I was playing. That was a few years ago, no noise to speak of.

How long has it been since you replaced the tubes? Preamp tubes can also create static and some other noises too. I doubt there is anything wrong with the amp unless it is still present with new tubes installed.

 

[Jamme1961]

I would start with the preamp tubes- do you have an extra one to swap in - one at a time to check each 12ax7 ? It could be anything but a lot of times it the tubes. You can gently tap the tubes ( all tubes ) while the amp is on to see if you hear it. Good luck

 

[Dave47857]

this did not happen on my Mesa mark v but it did happen to my peavey. I had the speaker cable to close to the plug in and I thought for a couple days days that I ruined it but once I moved the cab over it sits on it quit it really could be something dumb.