Tremoverb Hell

[Smokebreak3]

This one has 380VDC at the input jack, which is the supply voltage for V1. Even with V1 pulled (or replaced), I have 380V at the grid, at the plate, at the cathode at V1.
The input jack is metal switchcraft, non isolated, but chassis is painted. When I remove the input jack and float it out of the chassis, I get 380VDC from the ground points to chassis.
If I connect input jack to painted chassis, all hell breaks loose if wiggled the right way, I'm assuming shorting HV to ground, popping , squealing.
I'm just not seeing how any component failures around V1 would put HV EVERYWHERE

tremvrb2.gif

[xtian]

We're not going to spot the issue on the schematic...this is a mechanical failure, a short of some kind, stray wire clipping or blob of solder. Get out the bright light and magnifying glass. You'll probably have to lift the PCB.

[Snicksound]

Check the tube socket for any sign of failures or arcing

Is there shielded wire? There's a non zero possibility that a previous "tech" put shielded wire with the shield connected to the plate or worse. It's not uncommon, lots of modded Marshalls are like this. Unfortunately shielded wire is rarely rated for that kind of voltage.

[Smokebreak3]

No doubt it's mechanical, but for HV to be everywhere is special
I though a shorted coupling cap off the plate could be a possibility.

Not seeing any arcing, but that is my fear that arcing occured and traces are shorted. I guess I'll pull the Rp and see what happens

[Smokebreak3]

And yep, there is shielded wire at the grid, that was one of the first things I did was pull of the shield ground, it's connected to the ground side of the 47K under the cathode cap

[Stevem]

You have two problems going on here.

Your second is that With only preamp tube v1 out and all the other tubes in you should not have 380 volts to begin with on the power supply side of that 220k plate load resistor feeding pin 1.

This is assuming that v2a pin 1 has the correct 280 volts or there about on it.

[Smokebreak3]

Hey Steve, thanks, I think you may have omitted the "first" problem in your response.

Also, thanks for pointing the voltage situation out. I was in "spongy" mode so plates were only 390, and only 10V was being dropped across the whole rail (with ALL tubes in).
Nonetheless, I've now realized that every single plate, cathode and grid of every single preamp tube has 380VDC on it. Do I have a shorted Electrolytic in the power rail? Somewhow bubbling up through circuit ground? I can't think of another explanation

[sluckey]

I think you have a bad ground connection. Should be easy to find with just your eyes and an ohmmeter.

[TUBEDUDE]

With HV everywhere, especially on the cathode, your return is not making it to ground. Check resistance from.cathode to negative HV filter cap. Then find where the connection is missing

[Smokebreak3]

Ok thanks all. The last 2 filters ground at the input jack, and I had a compromised connection to chassis there. I hit it w a dremel and its stable, which is what I should have started w this morning ;(
But isn't it slightly terrifying that if that connection to chassis gets lost, at the input jack, that there is 400v sitting on the ground of the input jack?