Bias resistors in parrallel on 5E3

[Lead Burner]

I built a Torres kit that has the Hammond transformers, both power and output. I used a Sovtek 5y3gt rectifier and ended up with 420VDC on pin3 of the power tubes and 28volts on the 250ohm 5watt resistor about 15watts per tube. I switched to an old RCA 5y3gt and the plate voltage came down to 383VDC and 22volts on the 250ohm 5 watt resistor about 12watts per tube. I put the Sovtek rectifier back and eventually switched the bias resistor to 470ohms to get the tubes to under 14 watts, then I jumpered a330ohm resistor in parallel with the 470ohm resistor and the plate voltage came down to 404vdc and 22v at the bias resistor. I calculated bias using 330ohms and it works out to be 12.7 watts per tube. The amp sounds great now, but why is this working and will it burn up the PT in the long run?

[booj]

eventually switched the bias resistor to 470ohms to get the tubes to under 14 watts, then I jumpered a330ohm resistor in parallel with the 470ohm resistor and the plate voltage came down to 404vdc and 22v at the bias resistor. I calculated bias using 330ohms and it works out to be 12.7 watts per tube.

Parralleling a 330 and 470 gives 193. That should run hotter than the 250.

What output tubes are you using?

[Lead Burner]

I am using Tung-Sol 6V6s. No red plating yet. The 330 ohm resistor alone was hotter than the two in parrallel. Thanks

[hasserl]

Uuuugh, go back to the RCA and put the 250ohm resistor back in.

[tubeswell]

Do what Hasse said

and also put a string of 5W zeners reverse-biased (banded ends pointing to ground) in series with the PT's High-Tension Centre tap to the ground 3 x 9V ones or 2 x 12 V, or even 2 x 15V ones. That should take the plate voltage down to about 350-360.

[Lead Burner]

Bias resistors in parrallel on 5E3

Thanks Tubeswell and Hasserl, I put the RCA rectifier back in and two 15V, 5watt zener diodes in series just like you said. The plate voltage is 360v and I have 23v at the bias resistor, this works out to be about 11.7 watts per tube. Thanks again.