Fuser over-temperature protection
To protect the fuser from excessive temperatures, the MFP has the following three protective
functions:
■ The CPU monitors the voltage of the thermistor. If the fuser temperature reaches 240º C (464º F)
or higher, the CPU turns off the relay (RL101) to interrupt the power to the fusing heater.
■ If the temperature of the fusing heater continues to rise abnormally and the temperature of the
thermistor (TH1) exceeds about 250ºC (482ºF), the relay 1 (RL101) opens up to cut off the
power supply to the fusing heater.
■ When the temperature of the heater exceeds about 250ºC (482ºF), the thermal switch (TP1) is
turned off to cut off the power supply to the fusing heater. In the rare instance that this happens,
the fuser must be replaced.
Figure 5-4 Fuser circuit illustrates the fuser circuit.
Engine-control system 89
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