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resistor on the output. The voltage will typically decline with time. When a
speaker is present, the DC voltage will be less than 10 millivolts.
2.
Turn the power off.
Set the Bias Current
At this step, you will set the bias pots for the correct bias current. You’ll repeat this for
both the left and the right channels. You’ll need a meter capable of measuring DC
millivolts. The correct bias current is indicated by a voltage of 10 millivolts. A couple of
small test clips will also be quite helpful, as well as a #1 Phillips head screwdriver. Here
are the steps.
1.
Power Off
2.
Turn bias pot fully counterclockwise (it should have already been set that way).
3.
Connect your DC millivolt meter to the wires that come out of the tops of R32
and R33 for the LEFT channel.
4.
Disconnect inputs and speakers from the amplifier.
5.
Power On. Wait 1 minute for the amp to stabilize. The DC voltage you read will
typically be less than 1 milliVolt.
6.
Use a #1 Phillips screwdriver to turn the bias pot clockwise. The action at first
will be quite slow, with little apparent change in voltage. Take it slow and easy,
continuing to turn the pot clockwise until you observe between 19 and 11
millivolts of DC voltage on the meter.
7.
Turn the power off and wait 3 minutes
8.
Go back to step 1, and repeat this process for the RIGHT channel:
a.
Connect the meter to R32 and R33 of the RIGHT channel.
b.
Adjust the RIGHT channel bias current for between 9 and 11 millivolts.
Figure 49-Measuring bias voltage, left channel shown
Note: Make sure that your clip leads only touch the resistor leads.
