Brother MFC8420 Service Manual page 235

CHAPTER 6 TROUBLESHOOTING
I-6 Black and blurred vertical streaks
Possible cause
Dirt on the
scanner glass.
Dirt on the CCD.
Corona failure
Dirt in the paper
feed system
Scratch on the
drum
Cleaning failure
Scratch on the
heat roller
NOTE:
• If you print the same pattern continuously, the drum will be worn and black vertical streaks
will appear on the paper.
• This problem may occur with noise due to the corona wire being dirty. In that case, clean
the corona wire with the wire cleaner.
User Check
(1) Clean the corona wire in the drum unit.
(2) Check that the corona wire cleaner is at the home position.
(3) Check that the toner cartridge is not empty.
(4) The drum unit may be damaged. Install a new drum unit.
(5) The toner cartridge may be damaged. Install a new toner cartridge.
Step Check
Is there any dirt on that?
1
Is there any dirt on that?
2
3 Is the vertical block streak
about 10mm wide?
(Check if the wire cleaner is at
its home position.)
4 Is the paper tray or feed
system on the drum unit dirty
with toner?
5 Is the drum surface scratched?
6 Is the drum surface dirty with
toner in streaks?
7 Is the surface of the heat roller
scratched?
Result
Yes
Clean the scanner glass.
Yes Replace the CCD.
Yes Return the wire cleaner to its
home position.
Yes Clean the toner off.
Yes Replace the drum unit.
Yes Replace the drum unit.
Yes Replace the fixing unit.
6-40
Remedy