Guys.....I have an EL 34 Aiken Intruder. I need to re-bias the tubes, but I don't know how. It has the little slots in the back to put the meter into, to read the output of each tube (I have the meter and know how to do that), and it also has the "bias" screw on the back, but I don't know how to do it. (Unlike my Komet which has the idiot proof knob on it). Can anybody help a brother out?