I have a Carvin RC210 which I usually biamp with a Carvin 115. Yesterday I was going to use it in bridged mode, and when I hit my strings I got a really bad distortion that seemed to make a "blat" sound like I pushed the speakers too hard. When I try it now it seems quieter but still sounds good. When I play it biamped it sounds a lot like it did before, if not exactly the same, but now occasionally the sound fades away and the returns. Any idea what I did? I don't have the money to take it to a repair shop, but I'm pretty handy with a soldering iron. I've tried wiggling the inputs and the speaker outputs to see if that's the problem. It's not the preamp tube. If I were to try to repair this myself, what would I be looking for when I open the amp up?