The Copy Has Uneven Density (Darker At Front); The Copy Has Uneven Density (Lighter At Front); The Copy Is Foggy (Overall) - Canon PC400 Service Handbook

CHAPTER 3 IMAGE TROUBLESHOOTING

4. The copy has uneven density (darker at front).

5. The copy has uneven density (lighter at front).

Cause
Scanner
Cartridge, Scanning
lamp
Transfer charging roller

6. The copy is foggy (overall).

Cause
Scanner
Scanning lamp,
Developing bias
Grounding spring
3-8
Step Checks
1 Clean the scanning lamp,
reflecting plate, and lens.
Is the problem corrected?
2 Press the Copy Start key, and
switch the copier OFF in the
middle of operation; then, open
the top cover.
Does the toner image on the
photosensitive drum before
transfer have uneven density?
Step Checks
1 Clean the scanning lamp,
reflecting plate, and lens.
Is the problem corrected?
2 Is continuity present between
photosensitive drum PCB and
grounding spring?
YES/NO Remedies
YES End.
YES 1. Replace the cartridge.
2. Replace the scanning
lamp unit.
NO Check the transfer charg-
ing roller.
YES/NO Remedies
YES End.
YES 1. Check if the scanning
lamp goes ON normally.
2. Check the developing
bias.
NO Check to make sure if the
grounding spring is prop-
erly attached in front of the
cartridge.