Panasonic UF-890 Service Manual page 224

f-θ lens
This amorphous plastic, molded lens is designed to provide parallel laser light across the surface of the
drum, providing a constant scanning speed.
Fusing and Paper Exit
Fuser Unit (431)
The Fuser Unit, consisting of the Fuser Lamp, Fuser Roller, Pressure Roller, Thermistor, and
Thermostat, bonds the toner into the paper using heat and pressure.
Fuser Lamp (408)
Located in the Fuser Roller is a Halogen lamp that serves as the heat source for the Fuser Roller.
Fuser Roller (414)
A Teflon coated roller supplies the heat for bonding the toner to the paper. The temperature of the
surface is kept constant at approximately 190°C (±10°C) (or 374°F).
Pressure Roller (409)
This converted PFA tube Silicon Rubber Roller applies pressure to the Fuser Roller, assisting in bonding
the toner to the paper.
Thermistor Assembly (405)
The Thermistor, a heat sensitive resistor, in contact with the Fuser Roller, monitors the surface
temperature. The temperature detected is used to control the ON/OFF switching of the Fuser Lamp. It
also acts as the primary overheat prevention device. A comparator circuit on the FCB PC Board acts as
a secondary overheat protection and becomes active at approximately 200°C (392°F).
Thermostat 2 (432)
A Thermostatic Fuse, part of the power line for the Fuser Lamp, provides an extra overheat protection by
opening when the Fuser Roller surface temperature reaches 230°C (446°F) and remains there for 1
minute. If the primary and secondary overheat protection does not halt the rise in temperature, the
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