Pops and thumps, possible bad transformer?

[vibrovox7reverb]

I've got a project amp that I've been working on out of a silverface vibrolux reverb, and I decided to improve upon the old grounding system in the amp and came up with one that was as star grounded as I could get, and in the process I decided to also move the totem pole e-cap stack from under the cap can to inside of the amp to reduce wire length some and so I could separate more stages from one another and prevent crosstalk. After I implemented the new system the amp started making a swelling noise and then a thump with the volume on zero after the standby switch was thrown.

The amp can pick up guitar signal and the signal will swell and then 'thump' back to no volume and start to swell again etc. I've gone back piece by piece and undone the entire grounding system I had initially developed and reverted back to the original power supply format and I still get the same problem now. I've replaced the rectifier tube with other known good rectifier tubes, I've re-tensioned the rectifier tube sockets, I've replaced power tubes with known good power tubes.

The only step I haven't taken yet aside from checking a transformer is replacing the filter caps. I've also noticed that every 'thump' generally either creates a bright blue light, tiny spark, or usually combination of the two inside one of both of the power tubes. The thumping never takes place until the standby is thrown, but sparking inside the tubes leaves me to believe that the problem may lie with one of the transformers, and I'm not sure which it would be, but I have a feeling that since bad things only happen once the standby is thrown that it's probably the output transformer.
A related question that I have is: Do transformers have a limit on how much capacitance they can handle? I assume that something I did during the process of the grounding scheme and power supply rework caused this problem, and that seems to be the only conclusion I was able to come up with that would lead to my amp continuing to behave this way.

Any help on what my be the root of this problem would be greatly appreciated.

[R.G.]

There is some small chance that an OT went bad on you.

However, if you just did a massive rewire and now it acts funny, the odds are that there is a wiring mistake that you haven't found or recognized yet.

The odd in favor of that being the case are ... huge...

Arcing inside the output tubes means that you're exceeding the internal voltage flashover limits. I notice that your post is free of any numbers indicating that you measured what the power supply voltage is doing before/during/after standby and a flash event. If that were my amp, I'd be very, very curious about what those numbers were.

[vibrovox7reverb]

I'm about to attempt to check the plate, screen, cathode, and grid voltage of the output tubes, but I have a couple quick questions first. The blue light comes from inside of the plates, and occasionally a spark is generated on the bottom thing that the plates are attached to (sorry I don't know what it's called), so I'm just looking for some guidance on where I should be checking voltages.

Also, I had planned on upgrading the OT anyway, so I did and the problem persists as you predicted, however I've also been back and forth over the wiring of the power supply, and it's just fine...every wire and cap has been replaced and extra care has been taken to make sure that each wire goes to the point it's supposed to. I'm beginning to run out things to fix, the only things left that could possibly be culprits in my mind are: tube sockets, standby switch, and power transformer. What else could be a problem? The thing has been returned to exactly how it was before the wiring "overhaul" (obviously in the loosest sense of the word imaginable), and I'm trying to figure out how to avoid causing this problem in the future.

[vibrovox7reverb]

Ok, here are my findings...there are no abnormal voltages either in the output or preamp stages nor are there any voltage surges, but when I tried to check voltages in the reverb recovery stage the amp squealed like you wouldn't believe, and when I connected to the reverb mixer the thump speed up. I forgot to mention that the thumps happen on a beat, so that may be important, and also due to cable length I didn't have the reverb tank connected which might have been why these things were happening.

[vibrovox7reverb]

More findings...with the reverb tank plugged in, I can't read any plate voltages or any voltages of any kind in the amp, and the thumping sounds like it is under a pillow, but still easily audible. The reverb recovery stage still causes a squeal, but the mixer didn't make it speed up anymore. Remove the tank, and everything is back to as it was above. I'm at a loss...maybe the reverb recovery stage is sending a signal to the phase inverter and therefore to the output tubes??? It thumps no matter where I set the reverb knob, and the volume is at zero.

[R.G.]

More findings...with the reverb tank plugged in, I can't read any plate voltages or any voltages of any kind in the amp,

So plugging in the reverb recovery tank... kills the plate voltages of the entire amp ... ??

Hmmm. Is it possible that something about the reverb recovery tank grounding is being connected somewhere it shouldn't, and the squeal/thump and other oddities are Mother Nature's way of whispering in your ear "Something's not connected right... "