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November 2003 © TOSHIBA TEC 16 - 11 e-STUDIO3511/4511 FUSER UNIT/PAPER EXIT SECTION
16
(6) Temperature detection configuration
Thermistor is a device whose resistance decreases as it detects a higher temperature. Thus its input
voltage to CPU changes and then CPU judges whether this change is normal or abnormal. If one of
the fuser belt thermistors is broken, the control circuit judges that the fuser belt temperature is ex-
tremely low and keeps turning the IH coil ON. As a result, the fuser belt temperature rises, and
possibly activates the thermostat which is a safety protection device. To prevent this in advance,
CPU works to detect whether each thermistor is broken or not.
Also, the thermistors constantly check the temperature of IH coil to prevent it from excessive heating
by IH circuit abnormality, LGC circuit abnormality or thermistor abnormality. The thermistors auto-
matically turn OFF the power when the temperature of IH coil exceeds the specified temperature.
139
138
137
PC4/AN4
PC5/AN5
PC6/AN6
CPU
+5
Front edge
thermistor
Main
thermistor
Sub
thermistor
+5
+5
Fig. 16-406