Phaser 6180MFP Multifunction Printer Service Manual 2-57Theory of OperationSelective Control on Paper TrayThe default tray is Tray 2. The preferred paper tray can be changed using themenu on the printer’s Control Panel: System > Tray Settings.Laser Unit Light Quantity ControlImage data is sent to the Laser Unit as an electric signal (data are expressedwith high and low voltage values), and the laser diodes convert the imagedata from electric signals to optical signals (data are expressed with blinkinglaser beams).Variations in light quantity of laser beams or variations in the optical system(such as lenses) or drum sensitivity cannot attain a proper electrostatic image.Therefore, the laser beam light quantity is monitored and controlled by thelaser diodes.The Laser Unit has four laser diodes for Yellow, Magenta, Cyan, and Blackrespectively and the beam intensity is automatically adjusted for each color.Process ControlFor stable printing, the parameters related to the image development must becorrected as necessary. The process control is performed in two methods,after every 25 cumulative prints or during a continuous run.■ Potential Control■ Toner Density ControlThe following controls supplement the above controls:■ High Area Coverage Mode■ Admix ModePotential ControlTo attain stable printing image density, the drum charging voltage, thedeveloping DC voltage, and the Laser Unit beam intensity are adjustedaccording to the developing capability of each color carrier that variesmomentarily. The adjusted drum charging voltage, the developing DC voltage,and the Laser Unit beam intensity are fed back to keep the printing imagedensity constant.The outline of controls is as follows:1. The Humidity/Temperature Sensor detects humidity and temperature.2. The patches of respective colors (Yellow, Magenta, Cyan, and Black) forthe potential control are generated and transferred on the Transfer Belt.3. The ADC Sensor (Density Sensor) detects the density of the patch on theBelt.
