Samsung ML-2250/XBG Service Manual page 34

4.3.5.9 Transfer
The charging voltage, developing voltage and the transfer voltage are controlled by PWM (Pulse Width
Modulation). Each output voltage is changeable according to the PWM duty cycle. The transfer voltage used when
the paper passes the transfer roller is decided by environment recognition. The resistance value of the transfer
roller changes due to the surrounding environment in the room or within the set, this change in resistance in turn
changes the value of the voltage due to loading. This voltage is fed back into the set through the A/D converter.
Based on this fed back value the PWM cycle is changed to maintain the required transfer voltage
4.3.5.10 Fusing
The temperature of the heat roller's surface is detected according to the resistance 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. The 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 controlling range while controlling the fusing process, the error stated
in the table occurs. (For the domestic model, the Q-PID method has been applied.)
• Error Type
Error
OPEN HEAT -When warming up it has been lower than 68°C for more than 28
ERROR seconds
LOW HEAT -Standby
It has been lower than 80°C for more than 10 seconds
ERROR
-Printing
Up to 2 consecutive pages : It has been lower than 145°C
For more than 4 seconds.
From 3 consecutive pages : It has been 25°C lower than the
fixed fusing temperature for more than 4 seconds.
It has been higher than 220˚C over 3 seconds
OVER HEAT
It has been higher than 220°C for more than 3 seconds
ERROR
4.3.5.10 LSU
The LSU consists of the LD (Laser Diode) and the polygon motor control. When the printing signal occurs, the LD
is turned on and the polygon motor is enabled. When the light sensor detects the beam, Hsync occurs. When the
polygon motor speed becomes a normal, LReady occurs. If these two conditions are satisfied the LSU is judged to
be ready. If the two conditions are not satisfied, the error shown in the table below occurs.
Error Type
Polygon Motor Error
Hsync Error
Samsung Electronics
Description
When the polygon motor speed doesn't become steady
The polygon motor speed is steady but the Hsync is not generated
Description
Summary of product
DCU LED Display
60 All LED blinking
62 All LED blinking
68 All LED blinking
DCU Display Value
95
96
Service Manual
4-13