Canon NP6251 Service Manual page 615

CHAPTER 11 TROUBLESHOOTING
21. The copy is blank.
Cause Step
Primary
charging
assembly
Developing
assembly
DC controller
PCB
Scanning lamp
Connector
Potential control
system
Developing bias
Main motor
(M1)
22. The copy is solid black.
Cause Step
11-84
COPYRIGHT © 1997 CANON INC.
Checks
1 Is the primary charging assembly
set securely?
2 Is the charging wire or the grid
wire broken?
3 Is the developing assembly in firm
contact with the drum?
4 Does the blanking exposure lamp
remain OFF while the scanner is
moving forward?
5 Does the scanning lamp remain
ON during copying?
6 Are the connectors of the PCBs
connected securely?
7 Is the control by the potential
sensor executed normally?
8 Is the contact of the developing
bias firmly in place?
9 •Is the 1st copy blank halfway?
•Is the 1st copy blank, does the
2nd copy have displaced registra-
tion, and does a stationary jam
occur in this condition?
Checks
1 Does the scanning lamp remain
ON during copying?
YES/NO
NO
YES
NO
NO
NO
NO
NO
NO
NO
YES/NO
NO
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
Action
Set the charging
assembly.
String the charging wire
and the grid wire newly.
Check the developing
assembly locking lever.
Check the DC controller
PCB.
See "The scanning lamp
fails to turn ON."
Connect them securely.
Replace the potential
measurement unit.
Fix it in place.
Replace the main motor
(M1).
Action
See "The scanning lamp
fails to turn on."