peavey bass amp makes a loud distorted noise about 5-10 minutes of playing

[modog]

Hi everyone, this is Modog, I got this used Peavey 400 Mark III series bass head, and after about 5 to 10/15 minutes of playing, it starts making this REALLY LOUD noise where I just have to quickly shut it off. Then I'll wait about a minute, turn it back on, and it's fine, till it starts crapping out again.So is this something maybe I can try to fix, or is it something more serious, where I have to take it into a shop? I am an electrician, and I know thats worlds apart from electronics, but I have some electronics "basics", and can use a tester, and understand diagrams, so can someone get back to me Thanx, Modog,.........ROCK-N-ROLL!!!!!!!!

[Enzo]

Ball up your fist and whack the top of the amp. Does that either stop the noise or make it start? This is looking for a loose connection. My initial reaction is that some part is cracked free of its solder leving the amp unstable.