Controlling The Primary Charging Roller - Canon NP6621 Service Manual

OPERATIONS AND TIMING
D. Controlling the Primary
Charging Roller
1. Outline
Figure 3-304 shows the circuit that controls the
application voltage of the primary charging roller,
and the circuit has the following functions:
• Turns ON/OFF the primary charging roller bias.
• Controls the primary charging roller bias to a
constant voltage.
• Switches the application voltage level of the
primary charging roller bias.
• Controls the application voltage of the primary
charging roller bias.
• Corrects the scanning lamp ON voltage level.
Composite power supply PCB
Main transformer
T1
DC controller PCB
3–38
24V
Rectifier circuit
T4
Current
detection
circuit
Figure 3-304
COPYRIGHT © 1998 CANON INC.
The main transformer (T1) generates the pri-
mary voltage controlled by U402.
Filter circuit
Voltage
detection
circuit
PCTRLS
Microprocessor
U402
PCURS
Q301 (master)
Microprocessor
CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
Primary charging roller
Photosensitive drum