Canon NP6317 Service Manual page 190

CHAPTER 10 TROUBLESHOOTING
2. Light image (even in dark areas)
3. Light image (very light overall)
Cause/Problem
Procedure
area
Transfer corona
assembly
Copy paper
• Lower transfer
assembly
guide plate
• Varistor
• High-voltage
transformer
• DC controler
PCB
Developing unit
pressure apply-
ing mechanism
Amount of
toner in devel-
oping assembly
Developing bias
10-26
1 Does the image quality improve after the basic
adjustment procedure is followed?
2 Switch the copier OFF during copying and
open the front door. Does the toner image on
the surface of the photosensitive drum (prior to
transfer) appear normal?
3 Are the corona and grid wires of the transfer
corona assembly installed correctly, and is the
corona wire height normal?
4 Does the image become darker when fresh
copy paper is used?
5 Is the resistance between the metal part of the
lower transfer guide and the feeder 0 ?
6 Is the developing roller of the developing as-
sembly pressing against the photosensitive
drum?
7 Is the surface of the developing cylinder coated
uniformly with toner?
COPYRIGHT © 1999 CANON INC.
Check
CANON NP6317 REV.0 APR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
Result Action
Yes End.
No Perform step 6 and subse-
quent steps.
No 1. Install the corona wires
correctly.
2. Adjust the height of the
corona wires.
3. Clean the corona wires.
4. Install the corona assem-
bly securely.
Yes 1. The paper may have ab-
sorbed moisture, so in-
struct the user about the
correct method of storing
paper.
2. Explain to the user that if
paper not recommended
by Canon is being used,
the image quality may be
slightly poorer.
Yes 1. Check if the lower trans-
fer assembly guide plate
is touching the spring of
the feeder wait.
2. Replace the varistor.
No Check the high-voltage
transformer and the DC
controller PCB.
No Check the pressure apply-
ing mechanism of the de-
veloping assembly.
No 1. If the problem is the
black developing assem-
bly, see sub-section
"ADD TONER indicator
does not go ON."
2. If the problem is in the
CT unit, replace the CT
unit.
Yes Check if the developing
bias is being supplied to the
developing cylinder.