2-6 Phaser 6250 Color Laser Printer Service ManualSelective Control; Paper PickUnless 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-sheetFeeder is identified as Tray 3.Laser Light Intensity ControlThe 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 foreach color automatically. Image data is transmitted to the laser diodes in the LaserUnit as digital signals. The laser diodes convert the image data from digital signals tooptical signals. The laser assembly monitors and adjusts the light intensity of the laserbeams to attain a stable electrostatic image. Variations in drum sensitivity mayprevent the system from obtaining a proper electrostatic image.Process ControlFor stable printing, the parameters related to forming both the electrostatic and tonerimage must be continuously monitored and adjusted by the printer. Parametercorrection and control over the entire printing process is called “process control”.There are two main areas of control:■ Bias Control■ Toner Density ControlTo 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 ControlTo attain stable image density, toner density is monitored for each color and the drumcharging voltage and biasing DC voltages are adjusted according to the monitoredresults for each color.The bias control adjustment is made immediately before the start of printing, if any ofthe 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.
