My amp has recently started cutting out, and I can't find an explanation for it. It will do it at random, but all the lights will stay on, it seems like it just gets a hell of a lot quieter.
What amp is it? Is it a tube amp? If so, how old are the tubes? Have you checked your cables?
It's a laney solid state amp. I've checked my cables, i even switched guitars to make sure it wasn't that either.
It could also be the jack in the amp, or a short in your cord(s). Try all your cords and see if that's the problem. If not, it could be the jack.
Now that I think about it, it happened shortly after I plugged my wah into my effects loop, but it didn't didn't seem to do anything but make a popping noise. Could this have ****ed up my preamp or something like that?