Roller Electrode Bias Control Circuit - Canon NP6260 Service Manual

CHAPTER 4 IMAGE FORMATION SYSTEM
DC bias voltage level control
The voltage of the DC bias is determined by the signal (DCBC) from the DC con-
troller.
• High-voltage remote signal (HVRMT) = 1
• Roller bias remote signal (ROED) = 1
• Developing DC control signal (DCBC) = 3 V or more or less than 12 V
The above condition turns on the AC bias switch circuit; when the output (DCBC)
from the DC controller PCB increases, the output of DC bias will also increase.
Reference:
To prevent separation of sheets of
copy paper in a high humidity envi-
ronment, you may change the fre-
quency of the developing bias in ser-
vice mode (*5*, HI-HUME). A lower
frequency will make the image as a
whole to become darker (but possi-
bly foggy), thereby facilitating sepa-
ration with the help of toner. (Keep in
mind that a low frequency can lead
to foggy images.)

4. Roller Electrode Bias Control Circuit

The circuit used to control the roller electrode bias is equipped with the following
functions:
a. Turning on and off the roller electrode.
Roller electrode ON signal
• High-voltage remote signal (HVRMT) = 1
Roller bias signal (ROED) = 1
Switch circuit goes ON
High-voltage transformer drive circuit goes ON
DC transformer T402 goes ON
The above condition supplies the roller electrode with a bias of about 1000 V; the
DC bias is not controlled to a specific voltage.
4-36
COPYRIGHT © 1997 CANON INC.
DC bias voltage level
(V)
600
0
CANON NP6560/NP6360/NP6260 REV. 0 NOV. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
3 11
DCBC signal input voltage (V)
Figure 4-209