Brother HL-1870N - Page 221

HL-1850/1870N SERVICE MANUAL
6-37
I-2 Dark
Possible cause Step Check Result Remedy
Ground
contacts
Corona failure
(contact failure)
1 Are the charge electrodes
between the printer body and
the drum unit dirty?
Yes Clean both electrodes.
(3)
Drum unit failure 2 Is the problem solved after
replacing the drum unit?
Yes Replace the drum unit
with a new one.
Toner cartridge
failure
3 Is the problem solved after
replacing the toner cartridge?
Yes Replace the toner
cartridge with a new
one.
High-voltage
power supply
PCB failure
4 Is the connections of the
connector between the high-
voltage power supply PCB and
the engine PCB secured
correctly?
Yes Replace the high-
voltage power supply
PCB.
Main PCB failure 5 Are there any disconnected
connectors?
No Replace the main
PCB.
Engine PCB
failure
6 Are there any disconnected
connectors?
No Replace the engine
PCB.
User Check
(1) Check the paper used meets the recommended paper specifications.
(2) Check the printers environment. High temperature and high humidity conditions
can increase the amount of background shading.
(3) Clean the corona wire with the wire cleaner.
(4) Try installing a new toner cartridge or drum unit.