Brother International HL-720 Service Manual - Page 75

No paper supplied, Insufficient output from high-voltage power supply unit

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M-4 No paper supplied Possible cause Connection failure of connector Panel sensor circuit Paper pick-up clutch solenoid (SL501) Step Check 1 Is the contact of connector P6 on the panel sensor PCB good? 2 Set paper on the manual paper tray and press the test print button on the operation panel. 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? Result Remedy No Reconnect the connector. No Replace the panel sensor PCB. Yes Replace the paper pick-up solenoid. M-5 Insufficient output from high-voltage power supply unit Possible cause High-voltage contact High-voltage power supply failure Step 1 2 Check Do any of the terminals on the highvoltage contacts have dirt or contact burns? Check the connection of the harness between the high-voltage power supply and the driver PCB is OK? Result Remedy Yes Clean the high-voltage contact. Yes Replace the highvoltage 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 Poor thermistor harness contact Blown thermal fuse Halogen heater lamp failure Thermistor failure Step 1 2 3 4 Check Are the connectors on the erase lamp PCB and the high-voltage power supply PCB secured correctly? Remove the fixing unit and measure the resistance between the input connectors. Is it open circuit? Remove the fixing unit and measure the resistance of the fixing unit lamp. Is it open circuit? Is the thermistor installed properly? Result Remedy No Connect the connectors securely. Yes Replace the fixing unit after unplugging the power cord from the power outlet. Yes Replace the halogen heater lamp. Yes Replace the fixing unit after unplugging the power cord from the power outlet. No Reinstall the halogen heater lamp.

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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.