Brother 1240 Service Manual page 143

M-8 Scanner failure
Possible cause Step
Harness 1
connection
failure
Power supply 2
input
M-9 Fuser failure
Possible cause Step
Poor thermistor 1
harness contact
Blown thermal 2
fuse
Thermistor 3
failure
Halogen heater 4
lamp failure
Heater harness 5
connection
failure
NOTE:
This problem will be cleared if leaving the printer power ON for ten minutes.
If the heater is cooled down sufficiently, this problem may be cleared by turning on the
printer power switch while pressing the panel button. Be warned, however, that this
operation will melt the fixing unit if the heater is hot.
Check
Is the connection of the
scanner motor connector P12
on the engine PCB secure?
Is the voltage between pins 1
(+24V DC) and 2 (GND) of
connector P12 on the engine
PCB 24V DC?
Check
Is the contact of connector P6
on the engine PCB good?
Remove the fixing unit and
measure the resistance
between the input connectors.
Is it open circuit?
Is the thermistor installed
properly?
Remove the fixing unit and
measure the resistance of the
halogen heater lamp. Is it
open circuit?
Is the heater harness
connector connected to the
low-voltage power supply PCB
and fixing unit secure?
6-21
CHAPTER 6 TROUBLESHOOTING
Result Remedy
No Reconnect the connector
securely.
No Check if +24V DC is supplied
between pins 2 (+24V DC) and
3 (+24V RET) of connector P5
on the engine PCB. If not,
check the power supply output
on the low-voltage power
supply PCB.
Yes Replace the laser unit.
Result Remedy
No Reconnect the connector.
Yes Replace the fixing unit.
Yes Replace the fixing unit.
No Reinstall the thermistor
properly.
Yes Replace the halogen heater
lamp.
No Reconnect the connectors
securely.