V4 fixed bias

[Denton]

I have a 74 VT22 and a 72 V4B. I just received a bias probe from Eurotubes so that I could see if the bias resistors are still holding up. I have a NOS quad of Sylvanias ready to go in one of the amps, but I definitely want to make sure all is well before sliding them in to one of these (prob the vt22)

Anyway, I set the meter as instructed for DCA 200ma. The results after some fluctuating some:

VT22 - 23.5

V4B - 29.8

Which one is in spec? I assumed they would both be the same since they're basically the same amp. The VT22 fluctuated down for a minute or two before settling in the 23.5 range. The V4B went down and then back up to 29.8.

hangman??

[Hangman]

Both of those are pretty low. Which is where ampeg seems to put these amps. You could bring them up to 33 ma, but I wouldn't go higher than that. That's about 60% max plate dissipation at idle. In the v4, that's where tubes seem to be happiest.