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2-16 Phaser 8400/8500/8550/8560 Color Printer Service Manual
Theory of Operation
Drum Assembly And Transfix System
The Drum Assembly and Transfix Module form the key portion of the printer
where imaging takes place. The Drum Assembly and Transfix Module are
separate, yet interrelated. This section discusses the Drum. The next section
provides more detail on the Transfix Module.
In operation, the image is rendered on the rapidly rotating drum. The
Preheater heats the media to prepare it for the image transfer process. The
heated media is then passed between the Drum (now rotating much more
slowly) and the Transfix Roller. The pressure applied by the Transfix Roller
transfers the image to the heated media. An encoder disk and sensor on the
left end of the Drum monitors the Drum’s speed and position.
The drum heater heats the surface of the Drum to about 60
o
C (140
o
F) for
imaging. The drum heater does not rotate. The heater is inside the drum, and
is controlled by the Drum Heater Relay Board. The drum heater consists of
two resistive heater coils that operate in series for 220 V and in parallel for
110 V operation. The Drum Heater Relay Board controls the series/parallel
operation. The Drum Temperature Sensor monitors the drum temperature.
The main board interprets the sensor’s signal and turns on the drum heater
and Drum Fan to heat the Drum, or turns on the Drum fan alone to cool the
Drum.
The Y-Axis Motor drives the Drum. Through a single reduction belt drive, the
Y-Axis Motor rotates the Drum at a high speed for imaging and a constant low
speed for image transfer. The Y-Axis Belt uses an active tension system to
allow the pulley to float while the spring actively adjusts the belt tension.
N
o
t
e
The drum rotates in different directions for each process.
■ Transfix CW
■ Maintenance CCW
■ Printing CCW
Preheater
Tranfix Roller
Paper Path
Drum
Drum Heater
s8500-019