HP 8000dn Service Manual - Page 125

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 5-23 on page 140) 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 message will appear on the display panel. If the toner cartridge is missing, will be displayed. Print Density Adjustment The HVPS 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. Drum Ground Primary Charging Roller Toner Registration/ Toner Sensor Developing Roller Bias Post Transfer Bias Transfer Roller Figure 5-4 High Voltage Power Supply Contacts Fuser Bias EN Power Distribution System 101