Canon NP6251 Service Manual page 607

CHAPTER 11 TROUBLESHOOTING
10. The copy has white spots (vertical).
11. The copy has white lines (vertical).
Cause Step
Fixing assembly
Primary
charging
assembly
Developing
assembly
Copy paper
Photosensitive
drum
11-76
COPYRIGHT © 1997 CANON INC.
Checks
1 Press the Copy Start key while
keeping the copyboard cover
open, and turn off the power
switch while copy paper is moving
through the feeding assembly. At
this time, does the copy image
before moving through the fixing
assembly have white spots or
white lines?
2 Clean the charging wire, grid wire,
and shielding plate of the primary
charging assembly. Is the problem
corrected?
3 Is the developing cylinder coated
with an even layer of toner?
4 Use fresh copy paper. Is the
problem corrected?
5 Are there scratches on the surface
of the photosensitive drum
corresponding to the problem in
the copy image in the peripheral
direction?
YES/NO
NO
YES
NO
YES
YES
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
Action
1. Clean the inlet (upper,
lower) of the fixing
assembly.
2. Check the upper roller
of the fixing assembly.
3. Check the take-up
mechanism (cleaning)
for the web.
4. Clean the separation
claw.
Clean the parts
thoroughly with alcohol.
If the dirt cannot be
removed, replace the
charging wire.
Check the blade edge of
the developing assembly
for paper lint.
The copy paper may be
moist. Advise the user
on the correct method of
storing paper.
Be sure to find out the
cause of the scratches,
and then replace the
photosensitive drum.
Cont'd