Step 2: Exposure - Lexmark C950 Service Manual

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Step 2: Exposure

The printhead LED generates a scan line of LED light. Image data received from the RIP card assembly

modulates this scan line, 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 scan lines are applied on

the negatively charged drum surface. Whenever the print controller sends a command to print a black pixel, the

printhead LED 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. This discharge/no discharge process creates an invisible, electrostatic image on the

surface of the drum. This image is called a latent image.

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If the surface of the charge roller is damaged (for example, if it has a nick or a pit), it will cause

the charge to be uneven on the photoconductor. This will cause a repeating mark on the

printed page. Check the service manual for the repeating marks table.

If the charge roller is severely damaged, the surface of the photoconductor will not be charged

properly, and heavy amounts of toner will be deposited on the photoconductor. This will cause

the printed page to be saturated with 100% of each color. The imaging basket will need to be

replaced sooner.

Drum Surface

Invisible Latent Image

Drum Surface