HP LaserJet 4v/mv Service Manual - Page 89

Printing from the Paper Cassette Paper motion begins when the DC Controller PCA, after receiving a PRINT signal, starts the Scanner Motor, the Main Motor, and the fusing heater. The Cassette Pickup Clutch (CL2) is energized for 0.5 seconds, the pickup roller and the registration roller rotate and feed a sheet of paper from the Paper Cassette to the Registration Position, where the registration roller is stopped by the Registration Clutch (CL1), if necessary, until the Scanner and Fuser are ready. The DC Controller sends the VSREQ signal to the Formatter PCA within a specified amount of time after the Pickup Unit Photosensor (PS501) is activated. The leading edge of the media is now ready to proceed to the photosensitive drum. When the print engine receives the VSYNC and VDO signals, the printing process begins. After the paper passes by the drum, and through the fusing unit, it triggers the Delivery Unit Photosensor (PS401). The paper is then fed through the output rollers and to the top output bin. Printing from the MP Tray The presence of paper in the Multipurpose (MP) Tray is detected by the MP Tray Paper Sensor (PS1). The intermediate plate pressurization solenoid (SL1) is then activated, releasing the plate which applies upward pressure on the paper, causing it to contact the MP pickup roller. The MP Pickup Clutch (CL1) turns on at this time, allowing the registration roller to rotate. This feeds the paper from the MP Tray to the registration position. The remainder of the MP Tray print process is identical to the cassette feed process, described above. Printing from the Optional Lower Cassette When printing from the optional lower cassette, any of the 250-sheet paper cassettes must also be in place. The Pickup Arm in the optional lower cassette feeds the paper upward through a guide slot in the 250-sheet cassette to the Registration Roller. Once there, the operation is the same as printing from a standard paper cassette. Paper Jam Detection The Pickup Unit photosensor (PS501) in the registration area and Delivery Unit photosensor (PS401) in the output area detect when paper is moving through the printer (see Figure 5-14 for sensor locations). If a paper jam is detected, the DC Controller immediately stops the printing process and causes a 13 PAPER JAM message to be displayed on the control panel. Functional Overview 5-27 Functional 5 Overview