I recently took possession of an older (Pre-fender) SWR Super Redhead 2x10 combo from my brother, and it has been giving me issues. Any time I play through it, it only sounds distorted, at any volume and any EQ setting. I can turn the tweeter off and it still is this muddy distortion sound. It has received some work in the past, but we have tried all we could think of to fix it, short of replacing major parts. The speakers are new, and sound fine when plugged into another amp. Also, if I play through headphones the tone sounds really clean; there's no distortion. Does anyone know what might be causing this problem and how to get it dealt with? Its a great sounding amp when its in working condition, and I'd hate to have to part with it.