Mark VII Volume Drop What Could be the Problem?

[MetalThrasher]

I was playing my Mark VII last night and as soon as I started playing the amp I noticed a huge decrease in volume (more that half of what it used to be). I didn't want to push anything so I just turned the amp off. What could the issue be causing this volume drop? Could it be a bad preamp tube?

 

[Racerxrated]

A bad preamp tube could easily be it. Try pulling a tube from another amp, and start rotating it in each pre spot on the VII. See if that fixes it. Personally, I'd think V1 might be the culprit. I've had that happen before in an EVH 5153 and V1 was the problem. New production tubes are iffy IMO.

 

[MetalThrasher]

A bad preamp tube could easily be it. Try pulling a tube from another amp, and start rotating it in each pre spot on the VII. See if that fixes it. Personally, I'd think V1 might be the culprit. I've had that happen before in an EVH 5153 and V1 was the problem. New production tubes are iffy IMO.

I'll try that tonight. This makes me realize that I should buy a few spare preamp tubes as well. What are some good preamp tubes to get for my Mark VII?

 

[dcburn]

My Friedman Twin Sister did the same thing.
Didn't end up being a pre amp tube like originally thought, it was a shorted out connection before the tube.

 

[Racerxrated]

I'll try that tonight. This makes me realize that I should buy a few spare preamp tubes as well. What are some good preamp tubes to get for my Mark VII?

Personally, I'd go for a vintage used pre...that test good of course, from a seller with good feedback on the Bay or Reverb. Chinese 6n4, or earlier 8th/9th gen always sounded great with the Marks I've had.

https://reverb.com/item/71651412-br...uare-foil-getter-shuguang-2000s-fast-shipping

Not cheap, but they sound great. You could also order direct from China, but they take a month to get here, but cheaper.....

https://www.aliexpress.us/item/3256...746952!sea!US!0!AB&curPageLogUid=BTqeHEPWyOGo

Those have round getters; the 6n4(military version; same as 12ax7) have square. But those are cheaper.

 

[pipboy90]

I'll try that tonight. This makes me realize that I should buy a few spare preamp tubes as well. What are some good preamp tubes to get for my Mark VII?

JJ 12AX7s are fine.

I had a similar issue with my Mark VII when I had it and it turned out to be a bad power tube. Flip the amp around, take the tube cage off the back and put it in standby for 30 secs then switch the power on again and look for signs of a bad power tube:

https://www.thetubestore.com/how-to-tell-if-your-tube-is-bad

Be ready to shut the amp off quickly if a tube starts glowing bright or red-plating.

Mesa should send you a new quad if you bought the amp new. Reach out to their customer service.

 

[RaceU4her]

this is why i just always have a level of anxiety with tube amps, you just know eventually that dreaded volume swell is gonna come