Brother Facsimile Equipment MFC7420 - Manual (Page 221)

Confidential 9-33
I-6 Black and blurred vertical streaks
User Check
(1) Clean the corona wire in the drum unit.
(2) Check that the 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.
Possible cause Step Check Result Remedy
Corona failure 1 Is the vertical block streak
about 10mm wide?
(Check if the wire cleaner
is at its home position.) Yes Return the wire cleaner to its
home position.
Dirt in the
paper feed
system 2 Is the paper tray or feed
system on the drum unit
dirty with toner? Yes Clean the toner off.
Scratch on the
drum 3 Is the drum surface
scratched? Yes Replace the drum unit.
Cleaning
failure 4 Is the drum surface dirty
with toner in streaks? Yes Replace the drum unit.
Scratch on the
heat roller 5 Is the surface of the heat
roller scratched? Yes Replace the fixing unit.
NOTE:
• If you print he same pattern (especially vertical streaks) continuously, electrostatic charge
performance of the drum will decrease temporarily and black vertical streaks may 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.