Calibrations And Adjustments - Classe Audio CAP-100 Service Manual

Calibrations and Adjustments

Bias adjustment:
Note: Bias adjustment should be made without any load connected to the amplifier's output, and no signal
connected to the amplifier's input.
1. Since it is impossible to connect a multimeter to both emitter's resistors in order to measure and adjust
bias without disassembling the heatsink from the chassis, we provided a test point to ease the bias
procedure. It is located near the bias trimpot.
2. Connect the positive probe of a millivoltmeter to the test point and the negative probe to the positive
speaker post of the channel to be adjusted.
3. Turn trimpots counterclockwise until it reaches 0 . A click should be heard.
4. Turn on amplifier, and let it warm up for 15 minutes on idle.
5. Adjust trimpot to get a 20mV reading.
6. Let the amplifier warm up for a 24 hours period with signal and load.
7. Remove signal and load, and reconnect the multimeter.
8. Readjust to 24mV.
DC offset:
Note: DC offset adjustment should be made without any load connected to the amplifier's output, and no
signal connected to the amplifier's input.
On these units, DC offset can't be adjusted. Measure DC offset using a voltmeter connected to the output
posts, scale setted to mV. DC offset should be less than 10mV.
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