Samsung SCX-4720F Service Manual

Also see for SCX-4520: Product guide Solution guide User guide User manual User manual

Contents

Service ManualSummary of Product4-20 Samsung Electronics4.5.5 LSUThe 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, thestatus bit of the LSU controller register becomes 1 ant the LSU is judged to be ready. If the two conditionsare not satisfied, the error shown in the table below occurs.Error DescriptionPolygon motor error When the polygon motor’s speed doesn’t become a normalHsync error The polygon motor’s speed is normal, but the Hsync signal is not created.4.5.4 FusingThe 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 thetemperature of the heat roller. The AC power is controlled by comparing the target temperature to the valuefrom the thermistor. If the value from the thermistor is out of the controlling range while controlling the fusingprocess, the error stated in the table occurs. (For the domestic model, the Q-PID method has been applied.)4.5.4.1 Error TypeError DescriptionOpen heat error When warming up, it has been lower than 68 °C over 25 secLower heat error • Standby:It has been lower than 100°C over 25 sec• Printing:- 2 consecutive pages: it has been lower than 145°C over 5 sec- 3 consecutive page: it has been 40°C lower than the fixed fusing temperature over 4 seconds.Over heat error It has been higher than 220°C over 3 seconds