Figure 3. Removable hatch plate
1)Allow the amplifier to warm up for at least 30 minutes.
2)Turn the preamplifier volume completely off so that no signal is entering the amplifier
3)Loosen the 2 captive screws on the top hatch cover.
4)Remove the hatch cover.
5)The bias tool is snap attached to the top deck cover behind the power transformer. Refer to Figure 1.
6)Locate the toggle switches and associated small potentiometers (they are blue and have a small screw in the top). There are four, one for each output tube. Note the biasing meter.
7)Make sure that all of the toggle switches are pointed towards the meter (run position). Begin with any switch, moving the switch into the “set” position. You will see that the meter will rise up to show that the tube’s current is now flowing through the meter.
8)Using the bias tool, slowly turn the screw on the potentiometer that is adjacent to the switch until the bias meter reads ~ 35 miliamps (mA). Turn the screw clockwise to lower the bias and counterclockwise to raise the bias. Note that there are two ends on the bias tool. Using the end with the recessed screwdriver will greatly facilitate this operation.
9)Flip the switch back into the “run” position thus disengaging the tube from the meter circuit.
6