Turning On And Off The Ac Component Of The Development Bias; Controlling The Voltage Level Of The Dc Component Of The Development Bias - Canon NP6218 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM

3. Turning On and Off the AC Component of the Development Bias

The microprocessor (Q512) on the composite power supply PCB generates the
ACBIAS signal (pulse signal) under the control of the microprocessor master (Q301) on
the DC controller PCB. In response to the signal, the development bias AC component
generating transformer (T301) turns on to add the AC component of the development
bias to the DC component for application.
• application frequency
• application voltage

4. Controlling the Voltage Level of the DC Component of the Development Bias

The copier modifies the voltage level of the DC component of the development bias
based on the following factors:
• setting of the Copy Density key
• output of the AE sensor
• position of the Copy Density Correction knob (VR302)
The copier controls so that the voltage of the DC component of the development bias
varies between –80 and –560 V (in actual terms) by varying the output of the BPWM
signal.
To ompensate increases in the
photosensitive drum, the copier is equipped with a copy density correction volume. You
may operate the volume (VR302) on the DC controller PCB to adjust the potential of the
DC bias for any increase in V
4-26
2400 Hz (approx.)
1300 Vp-p (approx.)
light potential (V
, thereby freeing the copies of fogging.
L
(to lighter)
Developing bias
(DC component)
-500
-400
-100
(darker)
Figure 4-205
COPYRIGHT © 1997 CANON INC.
) caused by deterioration of the
L
(to darker)
VR302
Darker
Medium
Lighter
5 (lighter)
Copy density
CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)