Theory of Operation
Phaser® 3500 Laser Printer Service Manual
8-5
Paper Feed Sequence
When the Main Board is ready to feed paper, it energizes the paper feed solenoid. The solenoid
armature releases the clutch and the pick-up roller makes one revolution. This drives the paper
to the feed and retard rollers. The feed roller and retard roller drive the paper to the registration
transport assembly which in turn drives the paper towards the transfer area. Before arriving at
the transfer area, the paper actuates the Registration Sensor.
Paper Transport
The registration assembly continues to drive the paper into the transfer area, where the image
is transferred from the drum to the paper.
After the image is transfered, the paper continues to the Fuser Assembly for fusing the image.
In the Fuser Assembly, the heat roller is heated by a heat element and the paper passes in
between the heat roller and the pressure roller, where toner is melted onto the paper forming a
permanent image. The temperature of the heat roller is monitored by a thermistor that sends
signals to the Main Board.
The Fuser drives the paper into the exit rollers and the exit rollers drive the paper into the
output tray. When printing the first side of a duplex print job, the drive direction is reversed
when the exit sensor is actuated. Paper is then directed into the Duplex Unit for printing on the
second side.
Paper Feed Drive
The drive for all rollers is provided by the Main Drive Motor and a series of drive gears. The
Main Motor is used for paper feed, fusing, and the duplex/exit roller reversal for 2-sided
printing. 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 feed
solenoid. There is a separate Developer Motor for the Print Cartridge.
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