Brother HL-720, Service Manual

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M-4 No paper supplied
Possible cause Step Check Result Remedy
Connection
failure of
connector 1 Is the contact of connector P6 on
the panel sensor PCB good? No Reconnect the
connector.
Panel sensor
circuit 2 Set paper on the manual paper tray
and press the test print button on
the operation panel. No Replace the panel
sensor PCB.
Paper pick-up
clutch solenoid
(SL501) Does the voltage between pins 1
(SOLENOID) and 2 (GND) of the
P6 connector on the panel sensor
PCB change from approx. 24 VDC
to 0V within the specified time? Yes Replace the paper
pick-up solenoid.
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 high-voltage
contact.
High-voltage
power supply
failure 2 Check the connection of the
harness between the high-voltage
power supply and the driver PCB is
OK? Yes Replace the high-
voltage power supply
PCB.
No Reconnect the
harness between the
high-voltage power
supply and the driver
PCB.
M-6 Fixing heater temperature not adjusted
Possible cause Step Check Result Remedy
Poor thermistor
harness contact 1 Are the connectors on the erase
lamp PCB and the high-voltage
power supply PCB secured
correctly? No Connect the
connectors securely.
Blown thermal
fuse 2 Remove the fixing unit and measure
the resistance between the input
connectors.
Is it open circuit? Yes Replace the fixing unit
after unplugging the
power cord from the
power outlet.
Halogen heater
lamp failure 3 Remove the fixing unit and measure
the resistance of the fixing unit
lamp. Is it open circuit? Yes Replace the halogen
heater lamp.
Thermistor
failure 4 Is the thermistor installed properly? Yes Replace the fixing unit
after unplugging the
power cord from the
power outlet.
No Reinstall the halogen
heater lamp.