Printer Self Repair

Fusing Temperature Control Circuit

The thermister (TH1) detects the surface temperature of the fusing heat roller, and input analog voltage into IC201-78. According to the detected temperature, the heater lamp (H1) is turned On or Off by the heater lamp On/Off signal, which is input by IC201-55, and controls the temperature of the fusing part.

The heater lamp is 450W. 3 different voltages are used according to the destination; 100V, 120V and 230V.

If the heat lamp is not turned off even when the thermister detects abnormally high temperature, thermostat turns off the heater current as soon as the temperature of the heat roller reaches 195 °C, and prevents the heat roller from increasing its temperature.

Main Control Board

Figure 2-14. Fusing Temperature Control Circuit

Figure 2-14. Fusing Temperature Control Circuit

When the power switch is turned on, warm-up starts after the printer performs initialization, then, the heater lamp is turned on. The heater lamp stays On until the temperature of the heat roller reaches about 185 °C, and the following temperature controls are performed.

□ Temperature control model

This mode controls the temperature to maintain 185 °C during printing and 105 °C during waiting mode. This mode goes to mode2 after 45 seconds.

Figure 2-15. Heat Roller Temperature Control

□ Temperature Control Mode2.

This mode goes to mode 3 after 208 seconds. The temperature of the fusing roller decreases gradually approximately from 185 °C to 175 °C.

□ Temperature Control Mode3.

This mode controls the temperature to maintain 175 °C during printing and 105 °C during waiting mode. Unless the upper cover is opened or error happens, this mode is maintained.