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Developing Bias Control Circuit
The bias voltage that is applied to the developing roller is controlled according to the
potential (8-bit data) set point by the developing bias potential setting command from
the controller.
When drum cleaning begins during the mechanism initialization process or when
printing begins, the 8-bit data that indicates the target potential is read into the CPU
from the data memory of the MPU board and sent to the developing bias control
circuit. This data is then converted into an analog signal by a digital-to-analog
converter (DAC), amplified to a voltage range of 0 to +12 V (DRL CONT) by an
operational amplifier, and sent to the high-voltage power supply. As the charged
portion of the drum passes the developing roller, the DRL REM (developing bias
remote ON/OFF) signal is asserted, and the high voltage power supply sends the
bias voltage to the developing roller. This bias voltage consists of a DC component
(+200 V to +600 VDC, and a superimposed 10.5 KHz AC component (variable
between 1000 to 2000 V P–P).
3–40
Electrical System and Adjustments
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