Xerox PHASER 7500, Service Manual

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2-6 Phaser 7500 Printer Service Manual
Theory of Operation
Electric Charge
The BCR (Bias Charge Roll) evenly distributes a negative electric charge on the
surface of the Drum that rotates at a fixed speed. This is performed in parallel for
each color - Yellow, Magenta, Cyan, and Black.
• The BCR is always in contact with the Drum and it is driven by the Drum
rotation. The BCR is a conductive roll that is energized by the negative DC
component of the AC voltage from the HVPS and charges the Drum surface
evenly with negative charge.
• The Drum surface is photoconductive (becomes a nonconductor when it is in a
dark place and a conductor when exposed to light) and its inner side is
composed of a conductor (aluminum cylinder).
• The Cleaning Roll cleans the BCR surface.
Negative Charge
Positive Charge
Conductor
Photoconductor
BCR
Cleaning Roll
HVPS
Drum Surface
Drum Surface Potential
-V
0
Drum
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