Super reverb tube bias

[Underwood]

Hello,
Last couple of times I biased my 1964 Super reverb, I have had trouble getting the bias up to where I want it. Just today I went to put some NOS GE's in it and it maxed out at 24 and 21 mv. I used to like it at about 40 mv, but lately I settle for 30 to 34. As you all know, some tubes will go to 50 and some 20 at the same setting on the bias pot. The resistor on the bias pot is 15k, so I must have changed out the stock 27k in the past. What resistor do I change to get some of these GE 6L6's to bias up in the 40 range and not max out at 24? I haven't had to work on it for a while and forgot.  THANKS!

[sluckey]

Replace the 470Ω on the bias board with a 1K.

[Underwood]

Thanks for the info! I had a feeling it was that one, but wasn't sure of the value. I figured I didn't want to change the 15k on the pot any lower.

[Latole]

" As you all know, some tubes will go to 50 and some 20 at the same setting on the bias pot"
-Underwood

This does not mean anything.
It's as if you were saying that some amplifiers sound more powerful and others less with the volume have the same position.

The power (for bias)  is always calculated taking into account the voltage of the plates
25 mv / ma X 500 volts will not give the same bias as 25 mv / ma X 350 volts

[sluckey]

Underwood, what voltage do you measure on pin 5 of the output tubes?

[sluckey]

" As you all know, some tubes will go to 50 and some 20 at the same setting on the bias pot"
-Underwood

This does not mean anything.
It's as if you were saying that some amplifiers sound more powerful and others less with the volume have the same position.

Sure it means something. That's a perfect example of a strong tube and a weak tube. Now what you said means nothing and has no relevance to this discussion.