HP LaserJet 4 Service Manual - Page 281

High Voltage Power Supply Assembly The High Voltage Power Supply Assembly provides the necessary voltages for the printer's electro-photographic processes. The +24B VDC supply is used to power the High Voltage Power Supply Assembly. A summary of the major components of the high voltage system, is given in the table below (see Figure 7-18 for High Voltage PCA layout). Table 7-29 High Voltage System Checks Checks Action Are the connectors for the Primary Charge roller, Drum Ground, Developing Bias, Toner Level Sensor damaged, corroded, dirty, or missing? Also check the Toner Cartridge. Visually inspect each item. If any are damaged, correct as necessary. Replace the High Voltage Power Supply if the connection is not repairable. Check that all wires are connected to their respective terminals. Are the HVPS connections bent or broken? Clean the terminals with alcohol only. Troubleshooting 7-51