Mark V 25 - Stange Problem

Hey All,

I am having an issue with my amp... maybe tubes?

I play through it for 15 minutes or so and the sound suddenly dies. If I listen real carefully I can hear the signal but it is very low level and distorted.
It does this on either channel, at any setting. If I turn it off for a minute it will come back on and be fine for a while then it will go quiet again?

Any thoughts?


Cheers, Mike

My thought is tubes for the first item to try. It could be a bad solder joint on the board as those usually surface after warm up. But try the tubes first.

I'm having the same problem, but it happens after a couple hours of operation. I've had the MV25 since they first came out and this issue just started during band practices. Suddenly the volume cuts out, you can hear the signal faintly with buzzing distortion, both channels. Full sound will come back, but then fades again. This would be a nightmare at a gig.

Tried to replicate at home, leaving the amp on for a couple hours and playing occasionally, but that didn't cause it. I'm thinking tubes as well, but since it only happens after a couple hours of heating up, replacing one tube at a time isn't going to easily source the bad one. May have to call the tech line. Anyone else experiencing this? Any other suggestions?

For trouble shooting I would replace the power tube first. If the issue returns replace all other tubes. Then if the issue returns take it in for servicing.

Divide and conquer.

I have a tube tester so my actual process would differ but if I did not have the tester the above would be the way I would handle the situation.

Thanks. That's what I thought I'd do as well. Start with the power tubes. Since it's so delayed and intermittent, trouble shooting will take awhile, and probably a few more rehearsals. Glad we don't have a gig coming up immediately. A tube tester would be awesome!

Yep, power tubes. They were finally failing more consistently. Weird, seemed to be both. I replaced one at a time which didn't work. Not till I replaced both, did it correct the problem.

My MarkV was having issues. I took it in and it was the power tubes. Best to have a spare set of tubes on hand if you gig a lot. I always carry a spare set. Actually I always take a backup amp...a Boogie F30. It's a little amp but it does the job.