3nity said:
Then i found this website: http://home.comcast.net/~machrone/bjr/bjbias.htm
They say to change R52 from 22K to 27-30K.
I changed to 30K....with this it should read around -13V but voltage wont change from -10V.
"The stock bias resistors in a green board BJr are R31 and R37, 22K and 33K respectively. (In the cream board, they're designated R52 and R51, also 22K and 33K respectively.)"
I was going to say R31 - make sure you have the right resistor ...
They've given you the right advice, sort of. I would probably just put a 22k trimmer in series with R52 (or R31), that should give you the right amount of range, and make it easier to adjust next time you change tubes.
Just lift one end of the resistor and insert a 10k or 22k trimmer in series. Now you can gradually raise the bias voltage and see if the hum goes away.
(If you raise the bias voltage too much, you will hear crossover distortion when you play the amp, so don't be tempted to add 'one for luck'. Just set it where the hum is acceptable.)
If you do this correctly and the voltage will not increase, there is a good chance that you have a bad tube which is sucking the bias voltage in through a leaky grid. Needless to say, you should discard that tube (or the pair) and start again.
(I have no way of knowing if you have done this kind of work before, so I will just remind you that tube amps contain potentially LETHAL voltages. If you are not confident that you can carry this out safely, leave the job to someone who is. NEVER WORK ON A LIVE TUBE AMP WITHOUT ONE HAND BEHIND YOUR BACK.
)