mesa mark 5 keeps blowing the V1 preamp tube

[K-mark5]

Guys, many of you have lots of experience with amp problems.

Apparently there's something off with my boogie mark5, during our last gige live, the amp just did not produce any sound. When I had a chance to look at it during a practice, the V1 was completely burnt out/white.



So, apparently the amp worked for like 2 practices, but then it just stopped producing sound.
I opened up the amp to take a look inside and the V1 was completely burnt out again, I mean totally white and even the glass was broken so I puled it out in two pieces..


Put in a new mesa 12AX7, all worked.. for about one practice session, then again, no sound.. again V1, totally smashed as if it tore apart

Put in another mesa 12Ax7... sounding great... yet again for one practice session and the DAMN f%&# it today again the V1 is blown..

If anyone has any idea- what may cause the amp to constantly blow the V1 preamp tube? I mean this is ridiculous I've changed 3 V1 tubes over the past 2 weeks. The weird thing is that it always performs great until the next session when I fire the amp up.

the worst thing is it's no longer covered by warranty so, I'd maybe have to find someone who would take a look at it. Is there something to look at in the first place?

 

[duesentrieb]

(Most) probably V1 is DC heated and something in the DC-heaters-circuitry wrong, so it gets too much volts and blows --> tech.

 

[thickwood]

Try a ax7 tube used in cathode follower circuits,NO new sencor or sovtek tubes will last a week in a cathode follower position.
I think rubys work and penta along with Ei tubes.
Try one of those those.

Im not sure you have a cathode follower but if it is i can understand as the marchall forums talk of the tubes that do hold up !

 

[K-mark5]

nope, there's certainly no cathode follower in the amp.

 

[glpg80]

(Most) probably V1 is DC heated and something in the DC-heaters-circuitry wrong, so it gets too much volts and blows --> tech.

This