i have a hand-me-down crate K80 XL 15" keyboard amp from my grandpa. when it works, it sounds good, but after about a half hour of use, it fades out, just as if i had flipped the power switch. after this, it fades in and out randomly. USUALLY, switching it of for an hour or so seems to reset the problem and give me another half hour or so of unadulterated playing.

i just wanted to make sure that this isnt a problem i can fix myself before i pay to have it fixed professionally. any ideas?