another bias method - measure the DCR of the output transformer,
hook a clip lead to the center tap,
measure each leg from center tap to brn or blu or whatever color they use,
lets say you have 40 ohms from red to brown (leg 1) and 38 from red to blu (leg 2)
lets say you are running EL34s at 65% power ,
EL34 plate disp is 25 watts, but they don't roll those like metal base Mullards anymore,
so make it 24 watts.
65% of 24 = .65 x 24 = 15.6 watts idle disp
how many plate volts, 500? watts is EI, 15.6 watts/E = I, 15.6/500 = 31.2 ma
back to the transformer and Ohms Law
38 ohms x I-ma = volts across transformer leg #1
40 ohms x I-ma = volts across transformer leg #2
38 x .0312 = 1.1856 volts
40 x .0312 = 1.248 volts
so clip volt meter across leg 1 and turn the pot
check leg 2 and compromise your readings
EL34s sound better biased hot, 6L6 likes 60% for clean punch, EL34 likes 65% for that Marshall sound,
don't be afraid of high voltage, you are not going to live forever, get in there and mix it up, get some excitement going, you cant enjoy a good shock after you make the transformation into the spiritual world, be a man, so what if you die? you get a brand new body, girls will seem exciting again, ;D