Automatic Density Control; Selective Control: Paper Pick - Xerox Phaser 7400 Service Manual

Color printer

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Table of Contents

Automatic Density Control

The printer uses a series of test patches printed down the center of the Transfer Unit

belt to monitor the density of toner being supplied to the Imaging Unit drums. The

test patches consist of a grouping of all four colors applied repeatedly to the Transfer

Unit belt at density levels of 15, 30 50, 70, 85, and 100%. During the adjustment

cycle, these patches are printed twice and the ADC Sensor voltage outputs are stored

as reference values. During the status cycle, the test patches are generated once and

the resulting ADC Sensor voltages are compared to the reference values obtained

during the adjust cycle. Differences in the adjust and status ADC Sensor values

indicate how much to adjust the amount of toner being dispensed for each color.

The following diagram depicts the Transfer Unit belt with the test patches.

Unless changed in printer setup, the default tray is Tray 2. Trays in the optional

1650-Sheet Feeder are identified as Trays 3, 4, and 5. The tray in the optional

550-Sheet Feeder is identified as Tray 3. If both optional feeders are installed, the

550-Sheet Feeder tray is identified as Tray 3, and the trays of the 1650-Sheet Feeder

are identified as Trays 4, 5, and 6.

The Phaser 7400 printer supports a maximum of 4 optional trays.

Theory of Operation