Lexmark W820 Service Manual page 75

4025-XXX
The Printhead also helps to clean and prepare the drum by scanning the surface of
the drum at the beginning of each individual printer cycle. This action discharges an
residual DC charge that may still remain on the Drum from the last print cycle.
3.
Develop
The toner contained within the EP Cartridge has a magnetic property that causes it
to adhere to the Magnetic Roll. The Charge Metering Blade (CM Blade) spreads the
toner into a very thin layer on the Magnetic Roll. Friction between the Magnetic Roll
and the CM Blade generates a small electrical charge that is transferred to the toner.
The surface of the Magnetic Roll is made up of a thin sheet of conductive material.
The HVPS supplies the Magnetic Roll with two voltages; a DC voltage and an AC
voltage. The DC voltage is used to transfer toner from the Magnetic Roll to the
surface of the drum. The AC voltage agitates the toner on the Magnetic Roll, making
toner transfer easier.
The Magnetic Roll maintains a negative DC electrical potential. Negative charged
areas of the drum have a lower electrical potential, or higher relative negative value
than the Magnetic Roll. Discharged areas of the drum have a higher electrical
potential, or lower relative negative value, than the Magnetic Roll. A discharged point
on the surface of the drum now appears less negative in relation to the negative
charge on the Magnetic Roll.
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General Information