2-6 Phaser 6250 Color Laser Printer Service Manual
Selective Control; Paper Pick
Unless changed in printer setup, the default tray is Tray 2. Trays in the optional High-
Capacity Feeder are identified as Tray 3 and Tray 4. The tray in the optional 500-sheet
Feeder is identified as Tray 3.
Laser Light Intensity Control
The Laser Unit in the Phaser 6250 printer has four laser diodes: one each for yellow,
magenta, cyan, and black. The diodes control circuits adjust the light intensity for
each color automatically. Image data is transmitted to the laser diodes in the Laser
Unit as digital signals. The laser diodes convert the image data from digital signals to
optical signals. The laser assembly monitors and adjusts the light intensity of the laser
beams to attain a stable electrostatic image. Variations in drum sensitivity may
prevent the system from obtaining a proper electrostatic image.
Process Control
For stable printing, the parameters related to forming both the electrostatic and toner
image must be continuously monitored and adjusted by the printer. Parameter
correction and control over the entire printing process is called “process control”.
There are two main areas of control:
■ Bias Control
■ Toner Density Control
To supplement these two controls, the following are provided:
■ High-Area Coverage Mode Control
■ Admix Mode Control
■ Toner Density Control (CTD) Sensor (ADC - Automatic Density Control)
LED light density setting.
Bias Control
To attain stable image density, toner density is monitored for each color and the drum
charging voltage and biasing DC voltages are adjusted according to the monitored
results for each color.
The bias control adjustment is made immediately before the start of printing, if any of
the following conditions is satisfied:
■ First print produced after the power on.
■ Cumulative print count exceeds 16 since power on.
■ A cleaning cycle is executed during continuous printing.
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