Xerox 3450B Service Manual - Page 44

Transfer Roller The transfer subsystem consists of the Pre-Transfer Lamp (PTL) and the Transfer Roller. The PTL exposes the drum surface after the latent image has been developed to lower surface potential of the drum. This provides enhanced transfer efficiency. The transfer roller provides a high positive potential on the back of the print media. This potential attracts the negatively charged toner image from the drum and deposits it on the surface of the print media. Fuser Assembly The Fuser Assembly contains the entire Fuser Subsystem and is a field replaceable Service Part. The Fuser Assembly contains the following components: ■ Heat Lamp and Heat Roller: a halogen lamp generates the heat for the heat roller. The Heat Roller melts the toner so it adheres to the paper. ■ Pressure Roller: provides pressure on the opposite side of the print media so the heat roller can embed the melted toner in the media. ■ Thermistor: monitors the surface temperature of the Heat Roller. This information is used to control the heat lamp and thus keep the heat roller at the correct temperature. ■ Thermostat: prevents overheat damage when unexpected system faults occur. Paper Feed Drive The drive for all rollers is provided by the main drive motor and a series of drive gears. When the main motor turns, all the paper path components also turn except the Pick-Up Roller. The Pick-Up Roller assembly includes a mechanical clutch, released by the paper feed solenoid. Paper Out Sensor The paper supply is monitored by the Paper Out Sensor. When the tray runs out of paper, the sensor will send a signal to the Main Board, the control panel LED will blink yellow, and the Paper Out message for the appropriate tray will display on the control panel. Theory of Operation 2-11