Brother 1240 Service Manual page 148

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 Clean the electrodes
at both sides.
Yes Clean the shaft and
the electrode.
No Check the connection
between the shaft and
the electrode.
Yes Replace the drum
unit.
Yes Replace the toner
cartridge with a new
one.
No Reconnect the
connector correctly.
Yes Replace the main
PCB.
Yes Replace the laser unit.
No Replace the high-
voltage power supply
PCB.
6-26
Ground
Remedy
contacts