So I picked up a Peavey Mark III Head from a guy off craigslist dirt cheap. Figured something would be wrong with it, but for the first few weeks it sounded great. No issues, awesome. But now I'm starting to run into some problems. Sometimes when I turned the amp on, it didn't make any sound or just a really low crackling. In order to get it to work most times I had to crank the pre- and post- gain knobs to +6. I was getting concerned I was going to blow my speakers out, but I figured it wasn't that big a deal at the time. Now the sound cuts out while I'm playing...if I can get it to make sound. And so the cycle continues. I thought it might be the inputs at first, but then I realized it couldn't be that because of the whole cranking the gain knobs deal. Now I'm starting to think it might be gain pots, but I have no idea. I really need some help here. I've got gigs coming up and I'm short on cash. I have almost enough knowledge to do it myself so I'll give it a go if you know anything.