Brother HL 1240 - B/W Laser Printer Service Manual page 136

CHAPTER 6 TROUBLESHOOTING
I-3 Completely blank
Possible cause
Developing bias
contact failure
Drum unit
Drum unit failure
Toner cartridge
failure
Scanner
harness
connection
failure
Main PCB failure
Laser unit failure
Step Check
1 Are the developing bias
contacts between the printer
body and drum unit dirty?
2 Are the drum shaft and drum
electrode of the printer body
connected correctly?
3 Is the problem solved after
replacing the drum unit?
4 Is the problem solved after
replacing the toner cartridge?
5 Is the scanner harness
connected securely?
(Check if there is any play in
the connection.)
6 Are printing signals being input
to the laser unit?
Is the problem solved after
replacing the main PCB?
7 Is the scanner interlock lever
damaged?
Is the scanner mirror broken or
loose?
Result
Yes
Yes
No
Yes
Yes
No
Yes
Yes
No
6-26
Remedy
Clean the electrodes
at both sides.
Clean the shaft and
the electrode.
Check the connection
between the shaft and
the electrode.
Replace the drum
unit.
Replace the toner
cartridge with a new
one.
Reconnect the
connector correctly.
Replace the main
PCB.
Replace the laser unit.
Replace the high-
voltage power supply
PCB.
Ground
contacts