Developing Bias Control Circuit - Printronix L5000 Series Maintenance Manual

Developing Bias Control Circuit

Bias voltage that is printed onto the developing roll is controlled by the target data
(8–bit data) set by the developing bias potential setting command from the controller.
When drum cleaning begins when initializing the machine or beginning printing,
8–bit data indicating target potential is read in from MPU board data memory to the
CPU, and is sent to the I/O board developing bias control circuit. This data is then
converted into analog by the D/A converter, amplified to 0–+12V voltage (DRL
CONT), and sent to the high–voltage power supply unit. The DRL REM (developing
bias remote ON/OFF) signal is asserted from the I/O board, in time with the charge
unit on the drum by the main charger reaching the access point with the developing
roller. This unit then outputs superimposed bias voltage of DC voltage (+200–600V)
and 2KHz AC voltage (variable between VPP = 1000 – 2000V) to the developing
roller.
Electrical and Wire Data 6–37