Tube amp project

[gui_tarzan]

Yep, I verified that. Both red/yellow wires together are reading 820v across them (end to end) and if I go from one of those wires to ground or one to the yellow/red (dominant color first) tap I get 410v so I know I have them oriented right.

[g1]

If that commercial electric meter is an M1015B be aware that it is only rated for 300V and not safe for what you are measuring.
Also, on the 300V range you have to read off the 50V scale and multiply by 10.

[g1]

The 5F6 has the first 2 caps in parallel. If you had this you would get the same voltage reading at both caps.
So maybe you have a totem pole arrangement like the AB763 Super?
You should really post a schematic of what you actually have, not what it is based on.
Have you tried another rectifier tube?

[gui_tarzan]

I should have said the 5F6 is the preamp and PI circuit I'm using on this. I'm using the filter cap board I made for my Bassman 100 following that schematic because I had it handy, so the first two caps are in series. My meter goes to 600v on both AC & DC so I guess those numbers could be wrong, but doggone it just seems like even at 500v on the first cap it's still way too high.

[g1]

The B+ is relative to the power transformer you are using, I don't think you have specified that.
So for the power supply we should refer to the Bassman 100 diagram?

[gui_tarzan]

Yes, sorry. It's been a hectic week. I'm using the PT from a DuKane 1A395 that had a pair of 5881s, a 5U4 and a 12AT7 and my filter caps are laid out on a board for a Bassman 100.

[g1]

So what is the B+ on the Dukane schematic?
Was the 500V on the first cap measured with all tubes installed?
What kind of idle current are the power tubes at?

[potatofarmer]

With a 410-0-410 transformer through a tube rectifier, ~500V doesn't sound unreasonable. Probably something like a 375-0-375 for 110V but at today's wall voltage... Anyway, since you're not using a transformer designed for a 5F6, the voltages listed on the 5F6 schematic don't apply.

The 1kV is worrying, but that's probably just a wiring error and (at least one) dead filter cap. Long-term though, you're adding three more preamp tubes than the original Dukane amp had. Have you checked the AC voltage across the heater pins with the tubes in? You might've gotten lucky, and Dukane might've used a PT with excess current capability on the heater winding but I wouldn't bank on it.

[gui_tarzan]

I can't find an actual 1A395 schematic anywhere and I've looked for hours upon end for it. The other DuKane amps I can find have 6V6s and are showing much lower voltages on the rectifier and the power tubes. I'm going to switch the tap to the 127v input and then check voltages again. My guess is something is either shorted out or I have something hooked up wrong even though I checked the layout several times. I think the best thing for me to do right now is to unhook the PT, take some readings, then start connecting things one at a time and see what I end up with. Then I can report that back to you guys.

I appreciate all the time and help you guys are giving.

[g1]

Just a reminder about what olddawg said about aluminum connected to steel. Make sure all your grounds run to the steel, don't count on grounds via mechanical connection between the two metals. Weird things can happen.

[gui_tarzan]

Yep, anything mounted on the aluminum has a ground to the steel part of the chassis.

[gui_tarzan]

I figured out that this has two different input leads: 110v and 127v. I hooked up the 127v lead tonight because my house voltage is consistently 122-124v. As I expected I no longer have 1100v to my filter caps and thus that voltage no longer exists (if it did to begin with) and I have the following voltages on the caps:

C1=247v
C2=506v
C3=505v
C4=441v
C5=434v

MUCH better! This is with a 5AR4C, a pair of 5881s, two 12AX7 and one 12AT7 in the circuit.

Right now I have a bias voltage of -21v and the anode to cathode on the power tubes is running 10v. Voltage to the power tubes on pins 3 & 4 both read 508v so I think there's still something not quite right.

There is 740v across both B+ leads which gives 370v to ground on each one. These are far more reasonable than I had the other day. I still have a steady 6.0v on the heaters even using this 127v lead so I think I'm in the safe zone now.

[gui_tarzan]

V1
1 - 269
2 - 0
3&8 - 1
6 - 292
7 - 0

v2
1&7 - 243
2 - 0
3 - 1
6 - 434
8 - 256

v3 (pi)
1 - 224
2 - 15
3&8 - 54
6 - 205
7 - 17

[g1]

You are showing the same voltages for pins 6&8 of V2 and V3, could that be a typo? Can you recheck those?
And do you have a complete schematic?
What circuit is preamp, what circuit is power amp?

[gui_tarzan]

I corrected the voltage readings in the previous post.

The board and layout is a copy of the Fender 5F6 with the filter caps and resistors on a separate board (for my Bassman 100). The attached pic shows where I changed the values of a couple of the caps and took out the extra inputs, everything else is the same as the schematic. And I now realize I made a mistake by putting .01 caps in instead of .1 Mallorys.

The power tube layout is the same with the exception of adding 470/1w resistors across 4 & 6 and the 1.5k across 1 & 5, again from the SR AB763.