Fuser; Heat Roll; Pressure Roll; Heater Lamp - Lexmark W850n Service Manual

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Fuser

Heat roll

The heat roll is a hollow metal tube with a coated surface. This tube is heated by the inner heater rod. The heat
is applied to the media passing between the heat roll and pressure roll, fusing the toner on the media.

Pressure roll

The pressure roll is a metal shaft coated with sponge rubber. Pressure is applied to the media between the
pressure roll and heat roll, pressing the melted toner against the media.

Heater lamp

The heater rod of the lamp is compressed of a quartz glass tube containing a heater coil. A terminal is mounted
to the end of the heater rod via a harness. Three heater lamps are provided: the main heater rod to heat entire
heat roll, and the sub heater lamp 1 and 2 to heat the central portion of the heat roll.

Thermostat

If the heat roll temperature exceeds the preset temperature, the thermostat cuts off the circuits of the main
heater rod and sub heater rods 1 and 2.

Center thermistor

The center thermistor monitors the surface temperature of the media-feed portion of the heat roll to control on/off
of the main heater rod and sub heater rods 1 and 2.
Rear
thermistor
The rear thermistor monitors the surface temperature at the rear side of the heat roll to switch the heater rod to
use.

Pressure roll thermistor

The pressure roll thermistor monitors the temperature of the pressure roll to control the idling time for fuser
warm-up before printing.
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