Toshiba e-studio 167, Service Manual, Page: 226 / 268

e-STUDIO167/207/237 © 2007 - 2008 TOSHIBA TEC CORPORATION All rights reserved
FUSER / EXIT UNIT
13 - 10
6) Temperature detection configuration
Thermistor is a device whose resistance decreases as it detects a higher temperature. Thus its input
voltage to A/D converter changes and then SoC 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 tempera-
ture is extremely low and keeps turning the heater lamp ON. As a result, the fuser roller temperature
rises, and possibly activates the thermostat which is a safety protection device. To prevent this in
advance, SoC works to detect whether each thermistor is broken or not.
Also, the thermistors constantly check the temperature of heater lamp to prevent it from excessive
heating by MAIN circuit abnormality or thermistor abnormality. The thermistors automatically turn
OFF the power when the temperature of heater lamp exceeds the specified temperature.
Fig. 13-5
STH-1A ADCD0
MTH-1A
SoC
A/D
converter
Side
thermistor
Center
thermistor
+5V
ETH-1A
+5V
Edge
thermistor
+5V