Canon NP6621 Service Handbook page 62

IMAGE FAULTS
18 The copy has blurred images.
Cause Step
Scanner 1
drive cable
Scanner rail 2
Scanner 3
drive
assembly
Photosensi- 4
tive drum
Developing
5
gear
Drum drive
assembly
19 The copy has horizontal fogging.
Cause Step
1
Scanning 2
lamp
Developing 3
assembly
roll
Developing 4
assembly
bias
Scanner 5
Feeding
assembly
3–16
Checks
Does the cable wound around the
cable pulley overlap while the scanner
is moving?
Or, is the tension of the cable too high
or low?
Is the scanner rail soiled? Is there any
foreign matter on the scanner rail?
Is the gear of the scanner drive
assembly chipped?
Is the problem noted at intervals of
about 9.4 cm?
Is the problem noted at intervals of
about 4.2 cm?
Checks
Is the problem noted at the same
location on all copies made in DI-
RECT?
Does the scanning lamp flicker while
the scanner is moving forward?
Is the developing assembly roll soiled
with toner, or is toner found on the
surface of the photosensitive drum
where the developing roll comes into
contact?
Is the developing assembly bias
applied normally?
Make a reduced copy, and compare it
against a copy made in DIRECT. Are
the locations of the problem different?
Yes/No Remedy
YES 1. Re-route the cable.
2. If the cable is twisted or
frayed, replace it.
YES Clean the surface of the
scanner rail.
YES Replace the gear.
YES 1. Check the drum drive
gear.
2. Check the end of the
drum (where the develop-
ing assembly roll comes
into contact) for scratches
or protrusions.
YES Check the developing
assembly.
NO Check the drum drive
assembly.
Yes/No Remedy
YES Go to step 5.
YES Check the scanning lamp.
YES Clean or, as necessary,
replace the developing
assembly roll.
NO Re-install the developing
assembly, and check the
wiring.
YES Check the scanner.
NO Check the feeding assembly.