amp humming loudly and not responding

[i love everyone]

awhile ago, my friend's old Randall bass head broke down, and he found out the part he needed to fix it was out of production. in the meantime, he bought a new head, and i've been using it as a power amp (from the preamp out of my Peavey to the effects return of the Randall). it's worked out well for a while, but today while i was playing, it suddenly started humming very loudly, and there was no response from the guitar. the speakers looked like they were pulled back about as far as they would go, so i turned it off. it did this once before while it was still used for bass, and the problem was a wire from one of the big caps on top was disconnected. that's not the problem this time, so i really don't know where to look. ideas?

we have it taken out of the chassis from the last time we took it to a tech, but i'm not sure that would affect it very much. any help would be appreciated.

 

[J Moose]

Re: amp humming loudly and not responding

Maybe DC on the output stage?

Speakers going in (or out) and staying there is bad.

Really really bad.

Maybe a bridge rectifier or caps... transformer? Maybe several things wrong too. One thing blew & took other componets along for the ride... Not uncommon.

 

[i love everyone]

Re: amp humming loudly and not responding

Maybe DC on the output stage?

Speakers going in (or out) and staying there is bad.

Really really bad.

Maybe a bridge rectifier or caps... transformer? Maybe several things wrong too. One thing blew & took other componets along for the ride... Not uncommon.

yeah, it might be one of the caps like last time, although i haven't gotten a chance to test them. it's in the power stage, because i disconnected the pre-amp rail and accidentally turned it on, and it did the exact same thing. how would i check the DC in the output stage?