HP 4550 Service Manual - Page 128

Tray 3 (500-sheet paper feeder) Power supply The printer supplies +24 V and +5 V to the paper feeder for power. The paper feeder is controlled by the DC controller. It does not contain a microcomputer (CPU) or a drive motor. Its rollers are controlled by the printer's pick-up motor (M2). Pick-up and feed system Three switches (SW3001, SW3002, and SW3003) on the paper feeder PCB detect the paper size and presence of a cassette. The DC controller activates the pick-up motor (M2) and turns on the paper feeder pick-up solenoid (SL3001) after the pick-up motor starts. The paper feeder pick-up roller is activated by the pick-up motor and picks up the paper. Once the separation roller separates the paper from any extra sheets of paper, paper is fed into the printer by the paper feeder feed roller and printer feed roller. The rest of the paper path is the same as that in the Tray 2 cassette (see Figure 5-26). Figure 5-30 Pick-up and feed system Table 5-4 Solenoids, sensors, switches Reference Description SL3001 Paper feeder pick-up solenoid PS3001 Paper feeder paper detection sensor SW3001 Paper feeder paper-size detection switch SW3002 Paper feeder paper-size detection switch SW3003 Paper feeder paper-size detection switch 126 Theory of operation C7085-90921