Canon NP6621 Service Handbook page 58

IMAGE FAULTS
12 The copy has white spots (horizontal).
Cause Step
Toner 1
Photosensi- 2
tive drum
Primary 3
charging
roller
4
Transfer 5
charging
roller
6
7
8
Copy paper 9
Scanner rail, 10
Scanner
cable
3–12
Checks
Remove the developing assembly,
and shake it several times. Is the
problem corrected?
Is the problem noted at intervals of
about 9.4 cm? (scratches on photo-
sensitive drum)
Is the problem noted at intervals of
about 5.1 cm?
Execute service mode No. 402
(primary charging roller cleaning). Is
the problem corrected?
Execute service mode No. 403
(transfer roller cleaning). Is the
problem corrected?
Is the problem noted at intervals of
about 5.1 cm?
Is there dirt, crack, or scratches on the
transfer charging roller?
Are the position and the condition of
the transfer charging roller pressure
spring normal?
Try fresh copy paper. Is the problem
corrected?
Is the problem noted at the same
location on all copies?
Yes/No Remedy
YES The toner may be inad-
equate; advise the user.
YES 1. Clean the drum.
2. If the drum has scratches,
replace the drum car-
tridge.
YES Check the primary charging
roller for scratches and dirt.
YES End.
YES End.
YES Check the transfer charging
roller for scratches and dirt.
YES Replace the transfer charg-
ing roller.
NO Correct or replace the spring.
YES The copy paper may be
moist; advise the user on the
correct method of storing
paper.
YES 1. Check the scanner rail for
foreign matter.
2. Adjust the scanner cable
tension.