Brother Facsimile Equipment MFC7420 - Manual (Page 222)

Confidential 9-34
I-7 Black and blurred horizontal stripes
User Check
(1) The drum unit may be damaged. Install a new drum unit.
(2) Check the paper used meets the recommended paper specifications.
(3) Clean the printer interior and the corona wire in the drum unit.
Possible cause Step Check Result Remedy
Ground
contacts
Scratch on the
drum 1 Are the horizontal stripes
at 74mm (exposure drum)
intervals? Yes The exposure drum was
scratched. Replace the
drum unit.
Toner stuck
on the
developer
roller 2 Are the horizontal stripes
at 37mm (developer roller)
intervals? Yes After printing several
pages, the problem will
disappear.
If not, replace the toner
cartridge.
Scratch on the
heat roller 3 Are the horizontal stripes
at 79mm (heat roller)
intervals? Yes Replace the heat roller.
Corona
contact failure 4 Are the charge electrodes
between the printer body
and the drum unit dirty? Yes Clean both electrodes.
(3)
High-voltage
power supply
PCB failure 5 Is the problem solved after
replacing the high-voltage
power supply PCB? Yes Replace the high-
voltage power supply
PCB.
I-8 Black vertical streaks (in a gray background)
Possible cause Step Check Result Remedy
Ground
contacts
Translucent
stain on the
scanner
window 1 Is there any dirt on the
scanner window? Yes 1) Clean the scanner
window.
2) If it is not effective,
replace the laser
unit.
Corona failure 2 Is the corona wire dirty? Yes Clean the corona wire
with the wire cleaner.
(2)