Explanation Of Circuits According To Function; Drum Surface Potential Control Circuit - Printronix L5020 Maintenance Manual

Explanation of Circuits According to Function

The following pages provide an introduction to the main electrical circuits of the
printer.

Drum Surface Potential Control Circuit

The drum surface potential is converted to 8-bit data by the analog-to-digital
converter (ADC) and the drum surface potential sensor.
Meanwhile, the target surface potential is set as 8-bit data by the surface potential
setting command from the controller, and stored in the data memory of the MPU
board. The 8-bit data sent from the drum surface potential measurement circuit is
compared with the target data read from data memory by the CPU, and based on
that comparison result, 8-bit control data is sent to the main charger current control
circuit.
The control data is then converted to an analog signal by a digital-to-analog converter
(DAC), amplified to a range of 0 to 12 volts (+HV1 CONT) by an operational amplifier,
and sent to the high-voltage power supply. Upon asserting the +HV1 REM (main
charger remote ON/OFF) signal, the high voltage power supply outputs a current
(+HV1) to the main charger. The magnitude of this current (100 µA to 1000 µA)
corresponds to the control voltage.
3–38 Electrical System and Adjustments