B-52 LG-100A Gain 2 Channel Problem (quiet, muddy)

[thepoisonedyouth]

I know my amp is a solid-state. I bought it off of eBay used (thought it was a pretty good deal, wanted to try out something solid-state since I'm not ready to go through with owning and maintaining a tube amp).
It worked right for a few minutes. The Gain 2 Channel sounded absolutely perfect.
But then, out of seemingly nowhere, the Gain 2 Channel went to crap and now is quiet and muddy.
Everything else is working fine.
There may be a few reasons this happened:
1. it's used, old, and dusty. It may just be its time.
2. Instead of running the sound through a traditional cab, I used a pair of standard studio headphones, with a 1/4" jack. I don't know if this could be the cause, as It's a solid-state head and I figured there shouldn't be a problem with using low-output.

If anyone could share some knowledge it would be helpful. I really want to get this rig going.

[Jazz P Bass]

I seriously doubt that plugging into the headphone jack caused Channel 2 to malfunction.

Without a schematic, there is not much that can be done from this end.

I would try to contact B-52 & request a schematic.

Welcome to B-52 Guitar Amplification

[g1]

Being that it's "used, old, and dusty", have you tried giving the controls on that channel a workout? If they are dirty and noisy/crackly when you turn them, it could be they just need cleaning.