Xerox PHASER 7500, Service Manual

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2-74 Phaser 7500 Printer Service Manual
Theory of Operation
Color Registration Control
Overview
The Phaser 7500 is a Full Color Printer that uses the tandem system, where each
color - Yellow, Magenta, Cyan, and Black has its own Drum and Developer Housing
Assembly. Because each color forms an image on their own Drum, which are then
overlayed to create one image, color shift may occur due to Drum misalignments,
skewed installation positions, and etc. The function to correct this problem is the
Color Registration Control or Regi Con.
Types of Color Registration Control
The Phaser 7500 provides the following types of control according to the
operation timings.
Closed Loop Regi Con
When the power is turned On or if the printer internal temperature has changed
since the last operation when the IOT is operating (when the Drums and belts are
rotating), a patch for the Color Registration Control is created on the belt for the
detection/correction of color shift.
The color shift is detected by the MOB Sensors (x2). A combination of rough
adjustments and fine adjustments are performed according to the conditions.
Open Loop Regi Con
The color shift for each color is calculated and corrected based on the changes in
the printer internal temperature at the heading of a page during the print job. This
correction is performed in both lateral direction (fast scan direction) and process
direction (slow scan direction).
Belt
MOB
Sensor
(x2)
MCU Board
LPH Controller
Drum (K) Drum (C) Drum (M) Drum (Y)
LPH LPH LPH LPH
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