Brother MFC-7450

1-13
Confidential
■ Error code 78
Fuser unit failure (The temperature sensor of the fuser unit is broken.)
■ Error code 79
No detection of the internal temperature thermistor.
■ Error code 7A
No detection of the main motor lock signal.
■ Error code 7B
Main PCB failure
Print Unable 78
See Troubleshooting and routine maintenance chapter in User’s Guide.
Step Cause Remedy
1 Fuser unit failure Replace the fuser unit.
2 Main PCB failure Replace the main PCB ASSY.
Print Unable 79
See Troubleshooting and routine maintenance chapter in User’s Guide.
Step Cause Remedy
1
Harness connection failure of
internal temperature thermistor
Check the harness connection of the internal
temperature thermistor, and reconnect it.
2
Internal temperature thermistor
failure
Replace the internal temperature
thermistor.
3 Main PCB failure Replace the main PCB ASSY.
Print Unable 7A
See Troubleshooting and routine maintenance chapter in User’s Guide.
Step Cause Remedy
1 Main motor failure Replace the main motor ASSY.
2 Main PCB failure Replace the main PCB ASSY.
Print Unable 7B
See Troubleshooting and routine maintenance chapter in User’s Guide.
Step Cause Remedy
1 Main PCB failure Replace the main PCB ASSY.