so i'm grooving through my ampeg ba210sp combo and all of a sudden the speaker cuts out (not a faulty instrument cable or input jack anywhere). we cut the jam short, come back a few days later and it works fine...for about 4 minutes. several days later, just as i'm about to lug it into my saturn to take it to get repaired, it plug it in and the sumbitch is working fine. i take it in anyways. the repair shop has it for 2 weeks and can't get it to replicate the problem. plug it in and start to jam, but then it fritzed out after another short session. what is the deal? the power remains on, but the speaker just disengages. any ideas?