Strange power section problem

[EETStudent]

Well, got a weird one here. I just went through and replaced some filter caps in one of my amps, cleaned up the wiring a bit and did a couple little things to tidy up the power section. Well, the first retry resulted in a blown fuse. Checked for continuity and realized the B+ was connected to ground somwhere. I solved that and everything seemed OK. I tried it again and I heard some crackling so I cut it off real quick. Couldnt find an issue with some ground and component checks, so I turned it back on standby to just let whatever was happening kinda blow itself up. Again I heard the crackling, but then it stopped and I heard a click. Fuse didnt blow, but then the strangest noise started coming out of the speaker. It sounded like something was charging up about to take off, like a plan or something. Within 3-4 seconds it got louder and louder and then extreme humming and beating and so I shut it off. What could this be? Keep in mind the fuse was a fast-acting one( all I have at the time) but meets the rating the amp specifies. And the on/off, standby switch is an old rotary knob. Where do I look?

[EETStudent]

i just observed that with the power off all of the heaters are grounded. Well, continuity tests read about 0.3 with the other probe grounded. This shouldnt be even though the power is off right? There is a center-tap coming out of the tranny for the heaters

[EETStudent]

just want to reiterate that everything seems fine. Even while the amp drains after cutting it off the voltages read fine, the heaters actually read fine too. All the necessary grounds are present. I suspect that the switch is the problem. That clicking noise has me thinking that. The switch has about 4 contacts for the different settings, how can I check them?

[EETStudent]

Wait, with standby on should the voltages be getting to the power tubes and preamp tubes???

[EETStudent]

ok ok, heres what Ive reduced it down to. The problem is fixed halfway. About that loud, obnoxious I solved it. The amp does work but it either a) hums horribly or b)has pretty bad hiss. The latter happens when I switch to choke filter, eliminating the input filter cap, which I suppose would explain the hum. Option A occurs when I introduce the input filter cap. A bunch of hiss and some occasional crackling. Im about 80% sure the wiring is all right, but with this off/standby/on/on switch there are wires everywhere. Still, it seems ok. After turning it on, switching back to standby and then to off both produce loud thumps and crackles. Thumps and crackles when turned off seems like a common issue, but I dont know what of. Any help at all??

[EETStudent]

Ah worked it all out. Initially(first post ago) i had my caps misplaced. They were nearly all in parallel with one another, resulting in terrible filtering. Then, the hiss was from a bad preamp tube. An actual leg came off. Go figure, all that power amp fiddling and it was a freakin preamp tube. Well, everything is in better shape than it was so it works out.

For the record, Im pretty sure Im the first user to complete a fully developed thread on his own, top to bottom.

[Enzo]

Way to go. And all that without ever telling us what it was you were even working on.

[EETStudent]

Ha it was an old, all tube Rauland PA that Ive modified to BF Bassman AB165/AA864 specs. I wanted an amplifier that really had some sag to it, and the power supply originally was completely stout. Got new parts in from Weber today, and sittin here now at oh, 4:30 in the morning, I finally get to hear them. I tell ya, when I figured out the problem was a bad preamp tube I couldnt help but to laugh. I was stumped for so long and I just knew I had checked/replaced every component possible. Now Im waiting for my relays(props Enzo)