HP LaserJet 4v/mv Service Manual - Page 168

Half Self Test Functional Check The electrophotographic process can be subdivided into the following stages: • Cleaning (removing excess toner from drum surface) • Conditioning (placing a uniform electrical charge on drum) • Writing (laser strikes surface of drum to create latent image) • Development (formation of the toner image on drum) • Transfer (charge to transfer the image to paper) • Fusing (heat and pressure to produce a permanent image) The purpose of the Half Self Test Check is to determine which process is malfunctioning. Perform the test as follows: 1 Initiate a printer control panel self test. 2 Open the Front Door after the paper advances half-way through the printer (about five seconds after the Main Motor begins rotation). The leading edge of the paper should have advanced past the toner cartridge. 3 Remove the toner cartridge. 4 Open the toner cartridge's drum shield to view the drum's surface. If a dark and distinct toner image is present on the drum's surface, assume that the first four functions of the electrophotographic process are functioning (cleaning, conditioning, writing and developing - see Chapter 5), and troubleshoot the failure as a transfer or fusing problem. If NO image is present on the photosensitive drum, perform the following functional checks: 1 Drum Rotation Functional Check. 2 High Voltage Power Supply Check. 7-32 Troubleshooting