My Peavey Ultra 410 just started crackling and fading in and out (kinda hard to describe) but while I was playing it just started to fade out and then it came back for a second and just kept going that while I was playing, so I turned it off haven't really tried to fiddle with it at all. I know enough about electronics and amps to where if I was able to narrow down what the problem was I could fix it myself, otherwise I'll have to take it in to get it serviced, which isn't a bad idea, but I've only had the amp since Feb 2009, so it's not event hat old. Any advice? I think it's probably the fuse and/or something having to do with the preamp tubes.
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It most likely to be the output valves. My amp does the same thing on and off, depending on the volume and the settings, but i haven't got round changing the valves yet.