1-64 Service Manual
4025-XXX
Fuser Components
The Fuser Assembly is made up of seven major components:
CAUTION: The Fuser can be extremely hot. Be careful when working with or around the
Fuser Assembly. Switch off the printer and wait until the Fuser has cooled before
attempting to remove or disassemble it.
1. Heat Lamp 1 (Main)
Heat Lamp 1 is a quartz lamp that is suspended inside the Hot Roll. When the AC
Drive switches AC voltage to Heat Lamp 1, the Lamp heats up and in turn heats up
the Hot Roll.
2. Heat Lamp 2 (Sub)
Heat Lamp 2 is a quartz lamp that is suspended inside the Hot Roll. When the AC
Drive switches AC voltage to Heat Lamp 2, the Lamp heats up and in turn heats up
the Hot Roll. Heat Lamp 2 switches on during a print cycle.
3. The Hot Roll
The Hot Roll is a hollow aluminum tube that is coated with a non-stick surface. The
Heat Lamp heats the Hot Roll to a temperature sufficient enough to melt dry toner.
There is a drive gear attached to one end of the Hot Roll. The Hot Roll rotates
against the Pressure Roll.
4. The Pressure Roll
The Pressure Roll is a metal shaft that is surrounded by a hard rubber roll. The ends
of the shaft rest in spring-loaded bearings. The Hot Roll presses against the
Pressure Roll. During the fusing step, paper passes between the rotating Hot Roll
and the rotating Pressure Roll.
5. The Thermistor (STS)
The Thermistor is a heat sensitive resistor [STS] that gently rides on the surface of
the Hot Roll. The Thermistor monitors the surface temperature of the Hot Roll and
sends information back to the I/O PWB and on to the MCU PWB. According to the
temperature information received, the MCU PWB either switches on or switches off
the Heat Lamp.
If the Fuser begins to overheat, the Thermistor functions as the first-stage overheat
protection; signaling the MCU PWB to cut all AC power to the Heat Lamp.
6. The Fuser Thermostat
The Fuser Thermostat is connected in series with the Heat Lamp AC circuit. The
Thermostat functions as the second-stage overheat protection. If the Temperature
Sensor fails to shutdown AC power to the Fuser, at a specific temperature the
Thermostat opens the AC circuit between the Power Supply and the Heat Lamp.
7. The Fuser Fuse
The Fuser Fuse is connected in series with the Heat Lamp AC circuit. The Fuse
functions as the third-stage overheat protection. If the Fuser Thermostat fails to
shutdown AC power to the Fuser, at a specific temperature the Fuser Fuse opens
the AC circuit between the Power Supply and the Heat Lamp.
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