Brother Facsimile Equipment MFC7420 - Manual (Page 212)

Confidential 9-24
M-8 Fixing unit failure
Possible cause Step Check Result Remedy
Poor
thermistor
harness
contact 1 Is the contact of connector
CN19 on the main PCB
good? No Reconnect the connector.
Blown thermal
fuse 2 Remove the fixing unit and
measure the resistance
between the thermostat. Is
it open circuit? Yes Replace the fixing unit.
Yes Replace the fixing unit. Thermistor
assembling
failure 3 Is the thermistor installed
properly?
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.
Heater harness
connection
failure 5 Is the heater harness
connector connected to the
low-voltage power supply
PCB and fixing unit
secure? No Reconnect the connectors
securely.
NOTE:
• This problem will be cleared if leaving the printer power ON for ten minutes.
M-9 Main PCB failure
Possible cause Step Check Result Remedy
Main PCB 1 Is it possible to print the
test page with the method? No Replace the main PCB.
Software bug 2 Does this problem appear
when printing specific data
or printing under a specific
environment? Yes Inform the Brother office of the
used specific data, printer
condition and system
environment.