Xerox Phaser 4500 Service Manual page 56

Theory of Operation
2-20
Laser Assembly Functional Parts
1. Start of scan PWB
2. Scanner assembly
Laser Control
The scanner motor turns on when it receives a signal from the controller, and
turns off after printing ends. The motor remains off in the standby and power-
saving states.
There are two faults associated with the scanner motor speed: U2-1 Laser
fails at warm-up, and U2-2, Laser fails motor speed.
Two other laser unit faults, U2-3 and U2-4, are associated with LD power. U2-
3 occurs when LD power is too high, and U2-4 occurs when LD power is too
low.
Transfer Roller Assembly
The transfer roller is held in contact with the drum of the print cartridge, and is
driven by the drum gear. When the paper moves between the transfer roller
and drum, the transfer roller applies a positive charge to the rear surface of
the paper. The negatively charged toner image is attracted by the positive
charge on the rear surface of the paper. Thus, the image is transferred from
the surface of the drum to the surface of the paper.
The detack saw, located on the transfer roller assembly, helps to separate the
paper from the drum surface.
1
2
3. Laser diode assembly
Phaser 4500/4510 Service Manual
3
s4500-012