New Mark V 25- Volume Dropout Problem

[Coleo]

Hello all, I purchased a barely used Mark V last weekend, brought it home, set it up and experienced a weird issue with the volume kinda rolling up and down intermittently. It went away for a couple sessions so I thought I had solved for it with a cable swap. Well it happened again friday, and so I returned it right to the dealer, and purchased a brand new one (love Mesas, so sick of trouble shooting used, tube swaps, etc.). So I figured that a brand new one should do the trick.

Same thing! It drops in and out, like an ocean wave, randomly crackling, etc. This is what I have done
- removed FX loop cables, direct to amp
-swapped direct input cable
- put power cable directly to wall

I am playing at apartment volume so it is quiet (10W). It is also setup with a speaker cable directly into a Mesa cabinet, 8 ohm to 8 ohm.

Any ideas here? replace all cables?

I'm at a total loss. That said, I love the sounds from this amp and want to start playing it. Thanks! 8)

 

[Don]

Sounds like a bad preamp tube.

 

[Coleo]

I know anything is possible, but 1 brand new and 1 used amp with the same issue? I guess the brand new one was on the floor...would abuse on floor cause this? I know tube amps are pretty sensitive.

Thanks

 

[Don]

It's possible that they both had a bad tube. It's always the first thing to consider when an amp gives you problems.

 

[jaslan]

I have had my MV for about five years now. I think I am on the 4th set of power tubes. It seems to me, that every time I put in new tubes or even when the amp was brand new or when I swap inner and outer pairs, I get some strange noises and behaviors occasionally during the first five or ten hours (I have had volume swells before, a revving engine sound, and a slow, continuous rise in microphonic noise that I had to shut the amp down for).
It always seemed to cure itself after the tubes "burn in". I don't honestly even know if there is anything factual about tubes burning in or needing to burn in but I just thought I would offer it. Of course, as I said, my experiences were always an occasional type of weirdness and it sounds like your volume swells may be more constant. Anyway, I probably really don't know anything about your issue. I do hope you figure it out though because it is a great amp.