Phaser 3140/3155/3160 Printer Service Manual
2-7
Theory of Operation
Laser Unit
The Laser Unit is the core part of the Phaser 3140/3155/3160 and is controlled by
the video controller circuitry of the Controller Board. The Laser Unit converts video
data received from the Controller Board into an electrostatic latent image on the
surface of the OPC drum. This is achieved by controlling the laser beam and
exposing the surface of the OPC drum to the laser light. A rotating polygon mirror
reflects the laser light onto the OPC drum. Each face of the mirror produces one
scan line. The OPC drum rotates at the same speed as the paper feeding speed. As
the OPC drum turns, the laser scans creating the full page image.
The Horizontal Sync (HSYNC) signal is created when the laser beam from the Laser
Unit reaches the end of the polygon mirror and the signal is sent to the Controller
Board. The controller detects the HSYNC signal and adjusts the vertical line of the
image on paper. After the HYSNC signal is detected, the image data is sent to the
Laser Unit to adjust the left margin on the paper.
Transfer Roller
The Transfer Roller applies a positive charge to the rear surface of the paper. The
negatively charged toner image on the Printer Cartridge OPC drum is attracted to
the positive charge on the rear surface of the paper, causing the image to be
transferred from the surface of the drum onto the paper. For more information, see
“Print Cartridge” on page 2-8.
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