Greetings!
I've got a 130w Mark III 260c combo from the 70s. Now I have trouble getting clean sound out of it. With low levels of volume, the amp sounds nice enough. When I have to raise the levels to compete with the band, the sound gets really distorted. As far as I know, the source of the problem is the pre-gain section. At the moment, I'm playing pre-gain at two and post-gain at eight. This way the sound remains rather clean but is close to being too quiet even in a small rehearsal room.
I'm not familiar with electronics so I don't know what might be the cause. I guess what I'm thinking here is that is it even worth it to take it to a repair service? Can something like this be tracked with relative ease, or could the whole thing just be falling apart here and there and you don't know before opening everything? While the amp is good enough for rehearsals, I'm not willing to spend much on it.
TIA for any info!