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Service Guide OL400
Chapter 2 Principles of Operation
2.3.05 Fuser Unit
The fuser unit heater is controlled by a thermistor, a comparator, an LSI, and a CPU to keep the
heat roller surface temperature within a predetermined range (about 150 degrees). A thermostat
within the fuser unit prevents abnormal temperature rises in the fuser unit if the thermistor fails.
NOTE:
The CPU checks for a blown or shorted wire in the thermistor at power-on , setting a fuser alarm if
an error is detected.
The CPU also sets a fuser alarm if the proper temperature is not attained within a specified period
of time after power-on.
Upon detecting a fuser alarm, the CPU will halt (after printing the current page).
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