Tweaking my Mark 3 bluestripe head. Couple of questions....?

[Paul Secondino]

Hi guys.
I have a Mark 3 blue stripe head I recently bought.It's a blue stripe with EQ,simulclass,reverb.

I'm trying out various tubes and am not afraid to take a bias reading. But I'm not confident to test for plate voltage. What should the plate voltage be? I'm guessing 500v or just under.

So far, I am testing out JJ 6l6's in the inner sockets and JJ KT77's and JJ E34l's in the outer sockets. RIght now I am getting 46mA from the KT77's.

 

[Boogiebabies]

I would bet that your PT is only putting 460 volts to the plates. If so, your running a bit hot. It is all realy dependent on the plate voltage. Under load it may be 440V. If it was 440 42ma would be 75% MPD. If the voltage was higher the max bias would be even lower. It sounds like your just reading the bias off pin 3. A Simul is factory set for -46V. You need a bias meter to see what the tubes are drawing because no matter how hot or cold your tubes are running, pin 3 will be -46 +/- 2V.