Brother HL 1240 - B/W Laser Printer Service Manual page 148

CHAPTER 6 TROUBLESHOOTING
I-20
Possible cause
Toner cartridge
failure
High-voltage
power supply
PCB failure
I-21 Horizontal lines
Possible cause
Paper feed roller
Paper cassette
contacts
Downward fogging of solid black
Step
1 Is the problem solved after
replacing the toner cartridge?
2 Is the problem solved after
replacing the high-voltage
power supply PCB?
Step
1 Are the feed roller shaft and
the ground contact connected
correctly?
2 Are the ground contacts on the
back side of the paper cassette
connecting correctly?
Check Result
Check Result
6-38
Remedy
Yes Replace the toner cartridge.
Yes Replace the high-voltage power
supply PCB.
Remedy
No Check the connection
between the shaft and
the ground contact.
Also check the ground
contact on the back of
the feed roller. Refer
to P.4-24.
No Clean the contacts.
Ground
contacts