Hey GB&C! Figured I'd ask the experts for some help.

So a used amplifier I have at work is having an issue and being the guitar/bass tech, I'm tasked with trying to "fix" it. Now I have some knowledge and experience wiring guitars, straightforward pedals, and the like, but am a bit lost with the inner workings of an amp and what may be causing certain problems.

Here's the culprit:
It's a mid-late 90's Peavey Basic 112 Bass Amplifier, 50W into 8 ohm (solid state). Decent amp, when it behaves.

Here's the problem:
After turning on power, works fine for about a minute as it should. After this first minute however, signal distinctly changes over to a "distorted" sound when notes are played. Not a normal hum at high volumes, but it seems like its fuzzy and distorted (there is a gain knob and is possible to intentionally drive this amp, but this is not what's going on). I think it sounds cool as a driven bass sound, but other than this first minute or so, I cant get a clean sound at all. I've cut all gain, had volumes high and low, even used the dB cut and no results, it's still there.

Originally I thought it may be the speaker, but like I said it's fine initially and then changes over. Now I think it might possibly be a malfunctioning cap or electrical component, and upon opening it up, found that one was "leaking". It's the large gray capacitor under the wrapped cord in the pics. Everything else seems to be in fine order. Could this be the issue??

I'll post some images. If you need another angle or the schematic, let me know.

Thank you guys, any info or advice is much appreciated.
further away.JPG
Replace the capacitor. Also, check the rectifying diodes and power transistors for shorts. Check all solder connections; could be a heat-related poor connection, which may be why it works fine at first, but acts up after it warms up.