Earlier tonight I purchased a used guitar(Epiphone G400) and a (used) Crate RPX15. Its a great little amp, but the "solo" or lead channel doesn't seem to be working. Clean works great, as well as all of the effects

If I turn up the gain knob all the way, I can hear the guitar, but its SOOO quiet. The level knob doesn't seem to be doing anything as I turn it back and forth, which is leading me to think that the level knob "pot" is bad? Does it sound like im heading in the right direction? Can anyone give me advice on how to test it? I have a voltmeter, and basic skills...

Any help would be appreciated. Thank you in advance.

& I hope its okay to post a link, if not I'm sorry... But this is the amp.