Brother MFC-9420CN Service Manual page 284

I-4 Ribbing
Phenomenon
Light print occurs on the right or left hand side of the image as shown in
Main Causes
(1) Slight tilt on the surface of machine installation table.
(Tilt should be less than 1°.)
(2) Toner amount in the toner cartridge PU is insufficient.
(3) Toner cartridge PU is not laid as level, and as the result, toner concentrates to one side.
(4) The back cover ASSY is not properly closed.
(5) The OPC belt is off the truck and gets deformed.
(6) Retract failure of the toner cartridge PU.
Countermeasures
(1) Confirm the machine installation table to be flat and appropriate.
(2) Shake the toner cartridge horizontally for several times to remedy the concentration.
(3) Replace the toner cartridge PU with a new cartridge PU.
(4) Close the back cover ASSY properly.
(5) Replace the belt cartridge PU with a new belt cartridge PU.
(6) Replace the developer retract solenoid PU with a new developer retract solenoid PU.
Fig. 9-5
9 - 2 8
print sample [4] of Fig.9-1.
1
Confidential