Xerox PHASER 7500, Service Manual

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2-72 Phaser 7500 Printer Service Manual
Theory of Operation
Process Control
The Process Control prevents changes to the image quality due to varying
temperature and humidity in the printer, and Drum deterioration. Two process
control include: Potential Control and Toner Supply Control.
Potential Control
The Potential Control of the printer sets the charge potential (DC voltage in the
BCR), the DC component of the developing bias potential (DC voltage in the
Developer) and the exposure potential (brightness of LED in the LPH).
The charge potential (DC voltage in the BCR) and the developing bias potential
are calculated based on the temperature and humidity in the printer, which are
measured by the Environment Sensor.
The exposure potential is calculated based on the temperature and humidity in
the printer, which are measured by the Environment Sensor, and the patch density
on the belt, which is read by the ADC Sensor.
The patch is a small image for Process Control that is created on the belt.
ADC Sensor
Using two LEDs for Black and Color, the ADC Sensor reads the patch density of
each of the two reflection paths, which have different light axis angles. The LED for
Black uses a mirror reflection light path and the LED for Color uses a diffused
reflection light path.
s7500-423
Belt
Position at Shutter (Closed)
(Reference Board Detection)
Reference Board Light
Path Switching Component
Built-in
Reference Board
Diffused Reflection
LED (for YMC)
Straight Reflection
LED (for K)
Common Receptor Element
Position at Shutter (Open)
(Reference Board Detection)