Phaser 6500/WorkCentre 6505 Service Manual Xerox Internal Use Only 2-45Theory of OperationHigh Area Coverage ModeA continuous printing of any image of area coverage exceeding the toner dispensecapability causes the toner density in the Developer to be lowered.The High Area Coverage Mode postpones the next page feed and dispenses extratoner during this time, if the toner dispense time reaches the specified valueduring a continuous printing.Admix ModeThe Admix Mode dispenses toner immediately to prevent the reduction of tonerdensity, whenever the value of the toner density control patch measured by theADC Sensor falls far below the standard value, by dispensing extra toner. If thetoner density level cannot be recovered after this operation, it is determined thattoner has run out.ADC Sensor Control FunctionThe ADC Sensor is a reflection type sensor that radiates light from its LED onto thetarget and detects the reflected light at its photoreceptor and outputs electricsignals responsive to the amount of the detected light.To ensure an accurate patch density measurement, the surface of the ADC sensoris cleaned to remove soil due to toner, etc., and the light amount adjustment ismade so that the reflected light amount satisfies the prescribed value, whencreating the patch for potential control and toner density control.Color Registration ControlThe printer uses a tandem electro-photographic system with Organic PhotoConductor (OPC) drums and direct transfer by the Transfer Belt. The images areformed on the individual drums of the respective colors and then overlapped toform one image. The color registration control calculates how much each colorregistration is shifted, and adjusts the Laser Unit write timing. The scan controladjusts all four colors in the process direction.Color registration control is determined from a change in inside temperature andthe print count at the time control is applied. This control is outlined as follows:1. With no toner on the Transfer Belt, the output value of the ADC Sensor ismeasured to determine the threshold value.2. The patches for color registration control are generated on the belt. Thesepatches are composed of 10 mm lines of K, C, K, M, K, and Y in this order bythe amount of four dispense counts, led by a BlackBlack trigger.
