Canon Image Reader-A1, Service Manual

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COPYRIGHT © 2001 CANON INC. 2000 2000 2000 2000 CANON iR5000i/iR6000i REV.0 JUNE 2001
CHAPTER 4 IMAGE FORMATION SYSTEM
4-11 P
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.
F04--202-01
WMUPR WMUP STBY
200˚C
Potential sensor
Primary charging
Grid bias
Vpc Vpc Vpc Vpc
VD
+6V
-6V
VD
VD
Correction
control
sequence start
Potential
control
sequence start
Previous
potential
VD VD VD VD
VD
Target VD
Target
VD
Fixing assembly temperature195˚C