The Copy Has Uneven Density (Darker At Front); The Copy Has Uneven Density (Lighter At Front) - Canon GP605 Service Manual

Cause Step
Potential
control,
Photosensitive
drum
Developing bias
control
4

The copy has uneven density (darker at front).

5

The copy has uneven density (lighter at front).

Cause Step
Developing
assembly
Scanner (dirt)
Pre-exposure
lamp
Developing
assembly
Charging
assembly, Copy
paper
COPYRIGHT © 1999 CANON INC.
9 Turn off and on the power switch. Check
the setting of the following in service
mode: VLIM and VDM of
COPIER>DISPLAY>DPOT. Is it as
follows?
VLIM: between 62 and 82
VDM: between 432 and 452
1 Perform the Image Adjustment Basic
Procedure. Is the problem corrected?
2 Are the developing rolls of the developing
assembly in firm contact with the
photosensitive drum?
3 Clean the scanning lamp, reflecting plate,
side reflecting plate, mirror, lens, and dust-
proofing glass. Is the problem corrected?
Is the transfer/separation charging
assembly fitted securely?
4 Is the light of the pre-exposure lamp even
during copying operation?
5 Is the toner on the developing cylinder in
an even coating?
CANON GP605/605V REV.0 JAN. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 13 TROUBLESHOOTING
Checks
Checks
Yes/No Action
NO Check the power
supply control system;
if normal, replace the
photosensitive drum.
YES Check the control
system for the
developing bias.
Yes/No Action
YES End.
NO Check the developing
assembly locking unit.
YES End.
NO 1. Replace the pre-
exposure lamp.
2. Replace the DC
controller PCB.
NO 1. Clean the edge of the
blade of the
developing assembly.
(dry wiping)
2. Clean the surface of
the developing
cylinder.
3. Check to see if the
toner inside the
developing
assembly is even.
YES 1. Clean all charging
wires once again,
and check the
position of the
charging wires.
2. Try replacing copy
paper.
3. Check the nip of the
fixing roller.
13-69