Brother HL 1240 - B/W Laser Printer Service Manual page 137

I-4 All black
(1) Clean the corona wire of the drum unit.
(2) The drum unit may be damaged. Install a new drum unit.
Possible cause Step
Corona failure 1
2
3
Harness 4
connection
High-voltage 5
power supply
PCB failure
Main PCB failure 6
User Check
Check
Is the corona wire dirty?
Is the corona wire broken?
Are the charge electrodes
between the printer body and
the drum unit dirty?
Is the laser unit connected to
the main PCB correctly?
Is the problem solved after
replacing the high-voltage
power supply PCB?
Is the problem solved after
replacing the main PCB?
Result
Yes
Yes
Yes
No
Yes
Yes
6-27
CHAPTER 6 TROUBLESHOOTING
Remedy
Clean the corona wire
with the wire cleaner.
Replace the drum
unit.
Clean both electrodes.
Connect the harness
between the laser unit
and the main PCB
correctly.
Replace the high-
voltage power supply
PCB.
Replace the main
PCB.
Ground
contacts