gui_tarzan wrote:I tried two different VOMs, a good one and a cheap backup unit and they read identical voltages. The transformer is out of a DuKane intercom amp that came with a 5U4 rectifier, a 12AT7 and two 5881 tubes. The B+ red leads read 365v to the CT and the yellow leads are 5v and both sets go to my 5AR4C rectifier tube.
The first cap reads 500v after a few minutes (it starts at 585v and drops to 500v) and the positive lead on the second cap reads 1192v. That's WAY too high.
410 x 2.82 = 1156, its almost like it wired as a voltage doubler
Aaron wrote:Are you changing the multimeter to DC?
Aaron
No. I totally forgot that I'm dealing with DC at the filter caps. Now I'm going to feel like a real ass if that's the issue... I'll check that when I get home.
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 and preamp tubes:
C1=247v
C2=506v
C3=505v
C4=441v
C5=434v
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
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.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
