Peavey Mark V series amplifier problems

[Mike Bates]

I am following up on a post I made in mid-july.

I requested the cross to the output transistors, and I replaced the output
transistors, replaced the shorted driver transistors, and there is a common
problem I discovered later that causes these to go. The bias diodes were
almost open, and I replaced those.

I fired up the amplifier, and it was dead quiet, and it worked well!! thanks
for your advice.

anyway, about a week later of playing, the owner called me back up, and said
its got another problem.

based on what he told me, the amplifier developed a low-level AC hum, and it
gradually got louder and louder and louder within a few hours, and a loud
snap, and it got amazingly loud, with little distorted audio.

Based on this, the filter caps blew there tops. Why?

If this was a SMPS, i would understand why, but its just a conventional
power supply, and the only reason I would see the filter caps blow there
tops, is from increasing voltege over time. well, its not SMPS, and I dont
see how it would.

Any help? peavey experts? i had a local peavey expert tell me that the bias
diode was gone south, causeing the transistor failures, but hes still on
vacation.

Thanks.