SAMSUNG ML-2251N
Manual de Servicio

Summary of product

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 ERROR LOW HEAT ERROR Description -When warming up it has been lower than 68°C for more than 28 seconds -Standby It has been lower than 80°C for more than 10 seconds -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 It has been higher than 220°C for more than 3 seconds DCU 60 62 LED Display All LED blinking All LED blinking

OVER HEAT ERROR

68

All LED blinking

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 Description When the polygon motor speed doesn't become steady The polygon motor speed is steady but the Hsync is not generated DCU Display Value 95 96

Service Manual Samsung Electronics

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