Paper Feed Sequence; Registration Sensor; Paper Transport - Xerox Phaser 3425 Service Manual

Paper Feed Sequence

When the Main Board is ready to feed paper, it energizes the paper feed solenoid. The
solenoid armature releases the media unit clutch and the pick-up roller makes one
revolution. This drives the paper to the feed roller and retard roller. The pick-up roller
is designed with one flat side. The flat side always faces the paper supply when not
feeding paper. This shape allows paper to be moved in and out of the assembly.
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.

Registration Sensor

The Registration Sensor has two purposes. First, it is used to monitor paper
movement. If the paper takes too long getting to the sensor, or it stays at the sensor
location too long, the Main Board will shut down the machine, the control panel LED
will blink red, and a "Jam" error message will display on the control panel.
Second, the signal generated by the sensor tells the Main Board that the paper is
almost at the transfer area and it is time to start the xerographic process. It is
important that the leading edge of the paper enters the transfer area at the same time
as the leading edge of the developed image on the drum.

Paper Transport

The registration transport assembly continues to drive the paper into the transfer area,
where the image is transferred from the drum to the paper.
The paper continues to the fusing area where it goes between the fuser rollers. The
heat roller is heated by a halogen lamp. When the paper goes between the heat roller
and the pressure roller, the toner is melted into 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.
2-12 Phaser 3425 Laser Printer Service Manual