Brother mfc8440 - Page 232

MFC-8440/8840D/8840DN, DCP-8040/8045D/8045DN
SERVICE MANUAL
6-25
M-5 Insufficient output from high-voltage power supply unit
Possible cause Step Check Result Remedy
High-voltage
contact
1 Do any of the terminals on the
high-voltage contacts have dirt
or contact burns?
Yes Clean the terminals.
High-voltage
power supply
PCB
2 Check the connections of the
connector between the high-
voltage power supply and the
engine PCB are secured
correctly.
Yes Replace the high-voltage
power supply PCB
No Reconnect the connector
between the high-voltage
power supply and the engine
PCB.
M-6 Fixing heater temperature failure
Possible cause Step Check Result Remedy
Poor thermistor
harness contact
1 Is the contact of connector
CN7 on the engine PCB good?
No Reconnect the connector.
Blown thermal
fuse
2 Remove the fixing unit and
measure the resistance of the
thermal fuse. Is it open circuit?
Yes Replace the fixing unit.
Thermistor
failure
3 Is the thermistor installed
properly?
Yes Replace the fixing unit.
No Reinstall the thermistor
properly.
Halogen heater
lamp failure
4 Remove the fixing unit and
measure the resistance of the
halogen heater lamp. Is it
open circuit?
Yes Replace the halogen heater
lamp.
M-7 Laser Unit failure
Possible cause Step Check Result Remedy
Harness
connection
failure (1)
1 Is the LD harness connector
on the main PCB secured
correctly?
No Reconnect the connector
securely.
Yes Replace the laser unit.
Harness
connection
failure (2)
2 Is the polygon motor connector
on the engine PCB secured
correctly?
No Reconnect the connector
securely.
Yes Replace the laser unit.