Canon NP6621 Service Handbook page 64

IMAGE FAULTS
21 The copy is blank.
Cause Step
Drum 1
cartridge
Drum drive 2
assembly
Transfer 3
charging
roller
4
Composite 5
power
supply PCB
22 The copy is solid black.
Cause Step
1
2
Composite 3
power
supply PCB
3–18
Checks
Is the drum cartridge installed?
Is the photosensitive drum rotating
during copying operation?
Is the transfer charging roller installed
securely?
Is electrical leakage noted on the
transfer charging roller?
Is the setting in service mode 105
(primary current indication) 10 µA or
less?
Checks
Check according to "The scanning
lamp fails to turn ON."
Does the pre-exposure lamp remain
ON during copying operation?
Is the setting of service mode No. 105
(primary current indication) 10 µA or
less?
Yes/No Remedy
NO Install the drum cartridge.
NO 1. Check if the photosensi-
tive drum is rotating
smoothly.
2. Check the drum drive as-
sembly.
NO Install the transfer charging
roller securely.
YES Check the transfer charging
roller.
YES Replace the composite
power supply PCB.
Yes/No Remedy
NO Does the scanning lamp
remain ON during copying
operation?
NO Check according to "The
pre-exposure lamp fails to
turn ON."
YES Replace the composite
power supply PCB.