Brother HL-1850 Service Manual page 225

I-6 Black and blurred vertical streaks
Possible cause Step
Corona failure 1
Dirt in the paper 2
feed system
Scratch on the 3
drum
Cleaning failure 4
Scratch on the 5
heat roller
NOTE:
• If you print the 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.
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.
Check
Is the vertical block streak
about 10mm wide?
(Check if the wire cleaner is at
its home position.)
Is the paper cassette or feed
system on the drum unit dirty
with toner?
Is the drum surface scratched?
Is the drum surface dirty with
toner in streaks?
Is the surface of the heat roller
scratched?
6-41
HL-1850/1870N SERVICE MANUAL
Result Remedy
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.