Toshiba e-STUDIO453 Service Manual page 249

(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 roller thermistors is broken, the control circuit judges that the fuser roller tem-
perature is extremely low and keeps turning the IH coil ON. As a result, the fuser roller tempera-
ture 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 therm-
istors automatically turn OFF the power when the temperature of IH coil exceeds the specified
temperature.
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+5
Man
thermstor
+5
Edge
thermstor
Fig. 13-406
13 - 11
CPU
37
PC4/AN4
3
PC/AN
e-STUDIO350/352/353/450/452/453
FUSER UNIT / PAPER EXIT SECTION
13