Troubleshooting Image Faults - Canon PC920 Service Manual

C.

Troubleshooting Image Faults

1 The copy is too light. (halftone area only)
2 The copy is too light. (including solid area)
3 The copy is too light. (enter image, appreciably)
Cause Step
Lens, Reflect- 1
ing plate, AE
sensor, Static
eliminator
--------------- 2
Transfer 3
charging roller
Copy paper 4
Transfer lower 5
guide, Varis-
tor
Composite
power supply
PCB, DC
controller
PCB
Cartridge 6
Developing
bias, Develop-
ing bias
terminal
COPYRIGHT © 1999 CANON INC.
Checks
Clean the lens, reflecting plate, AE sensor,
and static eliminator. Is the problem
corrected?
Turn off the power in the middle of a
copying run, and open the machine's top
unit. Is the toner image before transfer
more or less normal? (Be sure to make a
check in a short time to protect the drum
from light.)
Is the transfer charging roller normal?
Try fresh copy paper. Is the problem
corrected?
Measure the electrical resistance on the
transfer lower guide plate and the side
plate (metal) of the fixing assembly. Is it
0 ?
Replace the cartridge. Is the problem
corrected?
CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 11 TROUBLESHOOTING
YES/NO
YES End.
NO Go to step 6.
NO 1. Mount the transfer
charging roller
correctly.
2. Replace the transfer
charging roller.
YES 1. The copy paper may
be moist. Instruct the
user on the correct
method of storage.
2. Inform the user that
using non-recom-
mended paper may
not bring the best
results.
YES 1. Check to find out if
the transfer lower
guide happens to be in
contact with a metal
part (side plate).
2. Replace the varistor.
NO 1. Check the transfer
high-voltage terminal
contacts for electrical
continuity.
2. Check the composite
power supply and the
DC controller PCB.
YES End.
NO Replace the electric unit
(composite power supply
PCB, DC controller
PCB).
Action
11-53