Determining Primary Current - Canon Image Reader-A1 iR5000i Service Manual

2.2 Determining Primary Current

To measure the dark area potential (VD) for the first time after the power switch is turned
on, the current used during previous measurement is let to flow, and the potential sensor is
used to measure the surface potential of the drum.
The DC controller PCB compares the surface potential of the drum against the target po-
tential; if the measured potential is ±6 V or higher than the target value, the primary current
is corrected, and the potential is measured once again. The potential is measured as many as
eight times, and the primary charging current is corrected as many as eight times.
Fixing assembly temperature195˚C
Potential sensor
Grid bias
Primary charging
COPYRIGHT © 2001 CANON INC.
Target
+6V
-6V
VD
WMUP
WMUPR
VD VD
Vpc
Potential
control
sequence start
F04--202-01
2000 2000 2000 2000 CANON iR5000i/iR6000i REV.0 JUNE 2001
CHAPTER 4 IMAGE FORMATION SYSTEM
VD
VD
VD
Previous
potential
Target VD
VD VD VD
Vpc Vpc Vpc
Correction
control
sequence start
200˚C
STBY
4-11 P