Ricoh FW780 Service Manual - Page 339

2.8 FUSING AND PAPER EXIT 2.8.1 OVERVIEW [A] FUSING AND PAPER EXIT Detailed Descriptions B047D102.WMF Two thermofuses [A] (184°C, 192°C) keep the fusing unit from overheating. Two thin-film thermistors measure the hot roller and pressure roller's temperature. The hot roller is a thin-shell, Teflon coated roller. The thinner roller allows a muchshorter warm-up time. However, extra care should be taken while working around the hot roller. It is very easy to damage. Like the A163/A251/A252 copiers, if the fusing temperature is lower than 60°C when the main switch is turned on, the machine assumes that it has not been used recently, and the main motor must rotate to generate the necessary triboelectric charge on the toner and developer. In the A163/A251/A252 copiers, the main motor begins rotating immediately. However, the B047/B048 copiers have a thin shell hot roller and a contact thermistor. When cold, the thermistor is hard and might damage the roller. The machine waits until the hot roller temperature reaches 80°C. At that temperature the thermistor softens and the hot roller can rotate safely. Except for the differences listed above, the B047/B048 copiers are identical to the A251 and A252 copiers. Please refer to A163/A251/A252 copier service manual for additional details. SM 2-7 B047/B048