I got a Fender '57 Champ reissue a year ago, this is the sound I was looking for, I really like it, so I'm extremely distressed that I hurt it. I got a new loop-recorder stomp box and like an idiot plugged it in and started pressing buttons, managed to turn the built-in metronome on with the level way too high -- loud distorted metronome sound and a lot of noise came out of the amp for about a second, and then silence.
Well, not exactly silence. The speaker is making the usual low hum, the power light is on, the rectifier tube and the power amp tube are glowing, but no guitar sound is coming out. It's obviously not the fuse because there's electricity getting to the power-on lamp, the big tubes and the speaker. And I figure that hum means the speaker is functioning. The guitar and cord work fine on another amp.
I can't see the preamp tube -- it has a metal covering so I can't tell if it's glowing or not. Before I start taking the thing apart to get the metal covering off, does is seem likely that the preamp tube is the problem? I haven't changed it since I got it a year ago and I play it quite a bit at a pretty high level. Are there other possibilities?
It's not the speaker -- that's connected to the circuit board with a 1/4" jack so it was easy to disconnect it and hook it up with an extension cable to the output from a different amp that's set up for the same resistance (4 ohms) -- the speaker works fine. It's also not the preamp tube, switched that out for a new one and it still doesn't work. I'm taking it to the shop tomorrow, I'll let you know what the diagnosis is.
As your thread is from 4 months ago, I'm assuming that you've taken it in and had it fixed by now. If not, what looper pedal were you using and how did you have it connected? Guitar In? FX LOOP? PreAmp Out/PowerAmpIn? Could be any number of things depending on what you were inputting to. I'm not familiar with the Input/Output options of the Fender Champ. I had a Twin Reverb back in the 70's but can't remember what it's configuration was now.