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9-2. Fusing Temperature Control
(1) Fusing Temperature Control Circuit
• The resistance of the Thermistor (TH) mounted to the Fusing Roller varies with tempera-
ture. The higher the temperature, the smaller the resistance value. The output from the
Thermistor (TH) is applied to the analog port of the CPU.
• When the temperature increases and the resistance of the Thermistor (TH) decreases,
the input voltage to the analog port becomes smaller.
• The CPU monitors the output from the Thermistor and turns ON or OFF the Heater Lamp
as necessary to control the temperature of the Fusing Roller.
• To energize the Fusing Roller Heater Lamp (H1), the CPU turns ON (LOW) the Heater
Remote output signal. This turns ON the triac in the Power Unit, which allows an AC volt-
age to be applied to the Fusing Roller Heater Lamp (H1) to heat it.
• When the temperature of the Fusing Roller runs inordinately high, the Abnormal Heater
Temperature Detecting Circuit is activated to shut down power to the Fusing Roller
Heater Lamp (H1).
AC
Input
A/D
CPU
Main Switch
Abnormal Heater
Temperature
Detecting Circuit
Heater Remote
On/Off
PWB-A (Main Board)
Power Unit
H1
H2
4131M060AA