High voltage values on V3; New member

[basisfunction]

Hi everyone,

I'm new here.

I'm trying to get a 100W Plexi Kit finished and I am having some problems. I have double checked my wiring and need some other ideas. I have included a spreadsheet with the volatges for my tubes this morning.

What I know:

A) Played a little through the amp, and get output through a cabinet. Gets moderately loud but not VERY loud. Tube distortion seems typical.

B) Lost the high voltage on one side of power tubes after blowing an HT fuse while checking power tubes. Replaced the fuse and finished making my handy chart. Pin 3 of two power tubes reads 0VDC and 6VAC for some reason after the fuse blown and replaced. Contunuity checks out with OT (broen wire fron OT) and other side (red wire from OT) is normal.

C)My original problem: V3 values very high, and seem to be approxiamtely double the voltage besides the heater connections which are normal.

D) Bias adjust does nothing anymore. Bias current is close to 43mA for all Power tubes.

E) Also, my filter caps read the following under power:

Under Board: 308V
By Fuses: 243V
56K 1: 488V
56k 2: 245V
3rd: 490V
4th: 386V

Any ideas? The V3 values were in this state under power BEFORE I lost half of the power stage today.

Thanks

Sam

[Flames1950]

For V3, check the resistor that the yellow wire going to pins 3 and 8 comes from -- should be a 470 ohm, but these high voltages are common when a 470K gets put in by mistake.

[basisfunction]

Ok, at lunch I checked and the particluar resitor was 470k. First mystery solved. You are spot on.

Sam

[basisfunction]

Fixed some minor errors. Couple cold solder joints, and the 470k in lieu of a 470. V3 voltages better, and perfect bias at 500V: 34, 35,35 and 34mA.

Wow.

Yay George!

Now to get some Webers....

Sam

[Flames1950]

Now to get some Webers....

Good call!!!! Might as well get it right, right from the start, eh?