Controlling The Surface Potential Of The Drum; Outline; Measuring The Surface Potential Of The Drum - Canon CLC 1120 Service Manual

CHAPTER 6 IMAGE FORMATION SYSTEM
B. Controlling the Surface Potential of the Drum

1. Outline

The surface potential of the drum is controlled for the following to determine the grid bias and
developing bias of the primary charging assembly:
· When the power switch is turned on while the temperature of the fixing roller is 130°C or
less. (drum surface potential control and dark area potential attenuation measurement)
· During last rotation for each copying run. (drum surface potential control only)
· During last rotation for every 2 hr. (drum surface potential control and dark area potential
attenuation measurement)
· When FUNCTION>DPC>DPC is executed in service mode. (drum surface potential control
and dark area potential attenuation measurement)

2. Measuring the Surface Potential of the Drum

The grid bias (Vg) of the primary charging assembly is set to the two levels of voltage shown in
Table 6-202, and the dark area potential when the laser is off (VD) and the light area potential when
the laser is on (VL) are measured by the potential sensor.
Using the VD/VL measurements and the grid bias (Vg), a graph like the one shown in Figure 6-
202 is prepared.
Vgl
-500V
Table 6-202
6-10
COPYRIGHT © 1999 CANON INC.
Vg2
-700V
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Drum surface
potential
Vd2
Vd1
VL2
VL1
Figure 6-202
Vd
VL
Grid bias
Vg1 Vg2