TRansatlantic Fizzing out

Hey. This is a ta15 question that I suspect could be a general amp problem, so I'm posting it here. My TA 15 has been fizzing out lately. It seems to happen if I Play for a bit and stop (like between songs). When I go back to play, it sounds really thin and fizzy and the volume is almost gone. Turning the amp off and waiting a few minutes before turning it back on usually fixes it, but it's getting to the point where I can't trust it live.

Any ideas?

Have ya checked the Tubes?

Never had that problem with my TA-15 although I had it with other tube amps.

I think Twally speaks the truth. Check those tubes.

I had my TA-15 do the same a couple of years ago, had'nt had it long. It was one of the output tubes. I replaced both. From what I've heard, EL84's aren't the most robust of tubes.