High Voltage Power Distribution The High Voltage Power Supply (HVPS, see figure 5-4) applies a DC- biased AC voltage to the primary charging roller and the developing roller, and a programmed DC voltage (depending upon the phase of the printing process) to the Transfer Roller. See the General Timing Diagram (figure 5-29 on page 145) for HVPS timing information. Toner Cartridge Detection A toner level detector inside the toner cartridge is connected to the HVPS when the toner cartridge is installed. If the toner level drops below a predefined level, the TONER LOW message will appear on the display panel. If the toner cartridge is missing, INSTALL TONER CARTRIDGE will be displayed.
Print Density Adjustment The high voltage power supply also controls the image density by varying the voltages applied to the developing cylinder in the toner cartridge. These voltages determine the amount of toner applied to the photosensitive drum. Print density is adjusted from the control panel (Print Quality Menu) or from the driver software. Primary Charging Roller Toner Registration/ Toner Sensor Drum Ground Developing Roller Bias Post Transfer Bias Transfer Roller Fuser Bias Figure 5-4 High Voltage Power Supply Contacts C4085-91087 Power Distribution System 95