Canon CLC 1120, Service Manual

Page: 164 / 901

CHAPTER 6 IMAGE FORMATION SYSTEM
6-12
COPYRIGHT © 1999 CANON INC. CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
5. Setting the Grid Bias and the Developing Bias
The grid bias and the developing bias DC component are determined using Vd/VL values, dark
area potential attenuation value, and target contrast potential value.
A line is drawn for the developing bias DC (Vdc) running through points representing the sum
of Vd and Vback voltages (for removal of fogging during copying operation; the Vback voltage is
set to 110 to 130 V according to the content of moisture measured by the environment sensor).
Then, a point where the contrast potential between Vdc and VL (Figure 6-206) is identical to
the target contrast potential is found, and the target values of the grid bias and the developing bias
are obtained.
Figure 6-204
The measurements of the surface potential may be checked by executing
FUNCTION>DPC>DPC in service mode (DISPLAY>DPOT); use the following as a guide in the
field:
Table 6-203
Image display Approximate guide
V00-500V 430 to 570
V00-700V 600 to 800
VFF-500V 50 to 150
VFF-700V 100 to 200
(V)
(V)
Vd
Vback
Vdc
VL
-520V
-370V
Drum surface potential/
developing bias
DC component
Target contrast potential
Contrast potential
Grid bias