Xerox Phaser 3250 Service Manual page 88

Phaser 3250 Laser Printer Service Manual
Driver
The Main Motor drives the Feed Roller, Developing Roller, and Exit Roller.
The BLDC Motor controls acceleration and steadiness of the Rollers. The
BLDC Motor is operated by the BLDC Clock and enable signal.
Transfer
The charging voltage, developing voltage, and transfer voltage are controlled
by Pulse Width Modulation (PWM). Each output voltage is changeable due to
the PWM duty cycle. The transfer voltage is used when the paper passes the
Transfer Roller is decided by environmental recognition. The resistance value
of the Transfer Roller changes due to the surrounding environment or the
printer, or the voltage value. This change in resistance in turn changes the
value of the voltage due to loading. This voltage is fed back into the printer
through the A/D Converter. Based on the value fed back, the PWM cycle is
changed to maintain the required transfer voltage.
Fusing
The temperature change of the Heat Roller's surface is detected according to
the value of the Thermistor. The Thermistor resistance is measured using the
A/D Converter and thus the CPU can determine the temperature of the Heat
Roller. AC power is controlled by comparing the target temperature to the
value from the Thermistor. If the value from the Thermistor is out of the
controlled range while controlling the fusing process, an error is reported.
Lamp Method
Error
Open Heat Error When the engine operates at the warm-up
Description
state, the temperature of the fixing unit is
not higher than a specified temperature.
When the error occurs, the engine stops all
functions and keeps it at error state.
Lower than 90° C for more than 10
seconds while warming up.
When the engine operates warm-up
process, if the temperature of the fixing
unit is not higher than a specified
temperature.
Theory of Operation
LED Display
All LEDs blinking.
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