Canon NP6621, Service Handbook, Page: 52 / 146

3–6
IMAGE FAULTS
2 The copy is too light (including solid black).
3 The copy is too light (overall, extremely).
Step
1
2
3
4
5
6
7
8
9
10
Yes/No
YES
NO
NO
YES
YES
NO
NO
YES
NO
YES
YES
NO
Cause
Transfer
charging roller
Copy paper
Lower transfer
guide
High-voltage
cord, High-
voltage trans-
former, DC
controller PCB
Toner, Toner
level detec-
tion mecha-
nism
Composite power
supply PCB
Drum cartridge
Transfer fault
Checks
Perform the Basic Image
Adjustment Procedure. Is the
problem corrected?
Turn OFF the power switch in
the middle of copying opera-
tion, and open the front door. Is
the toner image on the photo-
sensitive drum before transfer
more or less normal?
Is the transfer charging roller
securely installed?
Is electrical leakage noted on
the transfer charging roller?
Is dirt, cracks, or scratches
found on the transfer charging
roller?
Is the condition of the transfer
charging roller pressure spring
normal?
Try fresh copy paper. Is the
problem corrected?
Position the feeding assembly,
and measure the resistance
between the lower transfer
guide and the transfer charging
assembly rail (metal portion)
with a meter. Is the electrical
resistance 0 ý?
Take out the developing
assembly, and shake it several
times. Is the problem cor-
rected?
Is the setting of service mode
105 (primary current indication)
10 µA or less?
Remedy
End.
Go to step 7.
Install the transfer charging
roller securely.
Check the transfer charging
roller.
Replace the transfer charging
roller.
Correct or replace the spring.
1. The paper may be moist;
advise the user on the
correct method of storing
paper.
2. Advise the user that the use
of paper not recommended
by Canon may not bring
about the best results.
Check to find out if the lower
transfer guide is in contact with
the side plate of the lower
transfer guide or other metal
portion.
1. Check the continuity of the
high-voltage cord.
2. Check the high-voltage
transformer and the DC
controller PCB.
The toner may be inadequate or
the toner level detection mecha-
nism may be faulty; advise the
user on the correct ways to
handle the toner cartridge.
Replace the composite power
supply PCB.
Replace the drum cartridge.