Development - Lexmark W850n Service Manual

4024-110
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 a residual DC charge that may still remain on the Drum from
the last print cycle.
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Development

The toner contained within the PC Cartridge has a magnetic property that causes it to adhere to the Magnetic
Roll. The Metering 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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Diagnostic aids