Laser Scan Unit (Lsu); Transfer Roller; Fuser Assembly - Xerox Phaser 3500 Service Manual

Laser Scan Unit (LSU)

The Laser Scan Unit receives the bit-mapped image data from the Main Board and uses that
information to turn the laser beam on and off as required to correctly expose the drum. Image
data transfer from the Main Board is controlled by a synchronization signal from the LSU so
the vertical scanning line is synchronized with the printed page. The LSU contains the
following components:
■ Laser Diodes: Generates the laser beams.
■ Rotating Polygon Mirror: Scans the laser beam across the drum, axially.
■ Beam Detector: Synchronizes the left margin.
Optical Lens System: Focuses the laser beam onto the surface of the drum.
■
■ Mirrors: Reflect the laser beam onto the surface of the drum.

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 unit. The
Fuser Assembly contains the following components:
■ Heat Element and Heat Roller: A heat element 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.
Phaser® 3500 Laser Printer Service Manual
8-7
Theory of Operation