Lexmark 7462 series, Руководство по обслуживанию, Страница: 668 / 729

# Part
4 Waste toner collection
5 Drum
6 Developer roll
Charge
The charge roll places a uniform negative electrostatic charge on the surface of the drum. The drum surface is
made of a photoconductive material that holds an electrical charge as long as the drum remains in darkness.
Light striking the drum discharges the surface charge.
HVPS
(-VDC)
(-VDC)
Ground
Conductive Tube
Photoconductive
Surface
0V
-VDC value
DRUM
Drum Surface
Voltage
Drum Surface
Image
Ground
Charge roll
Exposure
The printhead generates a beam of laser light. Image data received from the system card assembly modulates
this beam, turning it on and off according to image information that is received from the host computer and
software.
Through the use of a series of rotating and stationary mirrors within the printhead, the beam scans the negatively
charged drum surface. Whenever the print controller sends a command to print a black pixel, the laser switches
on long enough to shine onto the drum at a single pixel point. That point is now discharged and slightly less
negative than the surrounding negative charge. The less negative areas are considered positive.
7462
Appendix C: Theory of operation
668