Brother MFC-9420CN Service Manual page 273

I-22
Phenomenon
A blank page (no print at all) is output or a specific color is missing (not printed) as shown in
sample [22] of Fig.9-1.
Main Causes
(1) The laser beam path is shielded by the paper.
(2) The toner cartridge is not sufficiently pressed in.
(3) The bias voltage of the transfer roller is not enough.
(Contact failure of the bias terminal of the HV power supply unit PU.)
Transfer unit cleaner PU
Transfer roller ASSY PU
Registration roller ASSY PU
Transfer unit PU
Paper feed roller PU
Countermeasures
(1) Check any paper or other foreign particles to lie in the laser beam path.
(2) Replace the toner cartridge PU with a new toner cartridge PU.
(3) Check the retract solenoid structure.
(4) Check if the transfer roller ASSY PU is installed properly or not.
(5) Replace the HV power supply unit PU with a new HV power supply unit PU.
White Print
Paper exit roller ASSY PU
Fig. 9-23
9 - 4 6
Belt cartridge PU
Toner cartridge PU
(K, Y, M, C)
Laser ASSY PU
Paper tray PU
Confidential
print