Xerox Phaser 8400 Service Manual page 46

The drum is driven by a closed-loop servo motor which, through a single reduction
belt drive, rotates the drum at a high speed for imaging and a constant low speed for
image transfer to paper. The Y-axis is on an active tension system, which allows the
pulley to float and the spring to actively adjust the tension during operation.
Single reduction
belt drive
Pulley
Tension spring
Warning
Always keep your fingers away from the drum drive system; it
uses a closed-loop servo drive system, which is inherently
dangerous. Since the motor speeds up if it senses the drum drive
system slowing down, fingers caught in the drum belts and gears
can be severely injured.
Theory of Operation
Y-Axis motor
Y-Axis
Encoder
Drum temperature
sensor
Fan
s8400-146
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