Brother MFC-9420CN Service Manual page 261

I-10
Phenomenon
Vertical line appears in the printed image as shown in
Main Causes
(1) Foreign particles (dust, etc.) adhere to the parts located around the OPC belt and the transfer
belt, and consequently contact the toner image formed on the belt surface.
Cleaning roller PU
Fusing unit FU
Transfer belt
Transfer roller
ASSY PU
Paper feed roller PU
Countermeasures
(1) Clean the stain of the belt cartridge PU.
(2) Clean the stain of the transfer belt.
(3) Remove the cleaning roller PU, and then clean the inside and outside of the waste toner
feeder.
Vertical Line
Transfer unit PU
print sample [10] of Fig.9-1.
Cleaning brush
Residual toner
Transfer belt
Fig. 9-11
9 - 3 4
Cleaning roller
Waste toner feeder
Transfer unit
cleaner PU
Drum
Confidential