Printronix L5535, Maintenance Manual

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II–116
Chapter 8
Photoconductive Section
Exposure
When the photoreceptor drum (which has been positively and uniformly
charged in the main charging step) is exposed to light, the exposed areas of
the photosensitive drum surface film go into conduction. Thus the charge in
the exposed area is neutralized while the unexposed portions of the drum
maintain approxi580 volts. The electrical pattern formed by this
process is called the “latent image.”
The printer draws on this principle. A bit-mapped image of the page, received
from the host computer, is contained in random access memory (RAM), on
the processor board. The image data illuminates the LED array, and the drum
rotates to form an electrostatic latent (invisible) print image on the positively-
charged surface.
The LED array consists of LED elements which are arranged in the direction
of printing width and related to printing pixels on a one-to-one basis. It
converts one raster (horizontal scanning line) of image data into a row of
illumination dots.
Dark Area Exposed Area
Light
Neutralized Charge
Se/Te Alloy
Photosensitive Film
Becomes Conductive
Aluminum Sleeve
Photoreceptor Drum
+
-
+ +
- -
Insulated
LED array
LED Array
Photoreceptor Drum
Electrostatic Latent Image