Problem with Mesa studio preamp: sudden loss in volume

[laurens]

I had a strange problem today with my Mesa Studio preamp. When I powered on, the output volume was less than 50% of the normal level (with my regular settings of course). Also, the sound of the preamp was still coming through even when I had turned the standby switch. So I hooked up my other preamp (Engl) to see if there are faulty cables or guitars, but that worked out fine. In the end I turned a few switches and when I did that with the switch for the loop level at the back (low - line) a few times, suddenly full power came back. That may be just luck.

3 weeks ago I replaced the preamp tubes with Mesa branded tubes. Power amp (2:90) also has new Mesa tubes. I had no problems up till now. This is freaking me out. What is the problem here? Dust or corrosion perhaps? Please advise.

 

[tonefreak25]

Just replaced the tubes?? Are you sure they are all still good?? I had a similar issue and it turned out to be my V5 tube,(the 12at7 reverb driver tube) had blown. I pulled it and everything worked perfectly. Just a thought, it could very easily be something else.

 

[laurens]

Just replaced the tubes?? Are you sure they are all still good?? I had a similar issue and it turned out to be my V5 tube,(the 12at7 reverb driver tube) had blown. I pulled it and everything worked perfectly. Just a thought, it could very easily be something else.

Maybe a noob question, but they seem to burn all fine. How can you see when one is faulty?

 

[tonefreak25]

You'll know, they will not light up or will look grey and or white inside and the filaments will be fried.
Try pulling the tubes one by one and seeing if you get any sound improvement,if so it may be a faulty, not blown tube or something to do with the tube socket. Just guessing here. Good luck!!