Canon NP6412 Service Manual page 344

CHAPTER 11 TROUBLESHOOTING
4 The copy has uneven density. (darker at front)
5 The copy has uneven density. (lighter at front)
Cause Step
Scanner 1
Toner 2
cartridge
Scanning
lamp
Transfer
charging
roller
6 The copy is foggy. (entire face)
Cause Step
------------ 1
Scanner 2
Grounding 3
spring
Scanning
lamp, Devel-
oping bias
11-58
COPYRIGHT © 1999 CANON INC.
Checks
Clean the scanning lamp, reflecting
plate, lens, and mirror. Is the problem
corrected?
Turn off the power in the middle of a
copying run, and open the machine. Is
the toner image on the photosensitive
drum before transfer more or less
uneven?
Checks
Is the density correction dial (VR107)
or the density adjusting lever set to the
middle setting?
Clean the scanning lamp, reflecting
plate, lens, and mirror. Is the problem
corrected?
Set the drum unit in the machine. Is
there electrical continuity between the
PCB of the base of the drum and the
machine's top unit?
CANON NP6512/6612/7120/7130/7130F REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
YES/NO Action
YES End.
YES 1. Replace the toner
cartridge.
2. Replace the scan-
ning lamp.
NO 1. Mount the transfer
charging roller
correctly.
2. Replace the transfer
charging roller
correctly.
YES/NO Action
NO Set the dial or the
lever to the middle
setting, and make a
copy. If the image is
still foggy, to step 2).
YES End.
NO Check to see if the
grounding spring is
mounted correctly (in
reference to the drum
drive gear).
YES 1. Check the activation
of the scanning
lamp.
2. Check the develop-
ing assembly.