Lexmark T652 Service Manual - Page 291

4062-XXX 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. Charge roll HVPS (-VDC) (-VDC) Ground DRUM Photoconductive Surface Conductive Tube Ground Drum Surface Image Drum Surface Voltage -VDC value 0V 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 negative 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. Diagnostic aids 3-79