Canon LBP-1210 Service Manual page 96

CHAPTER 2
If the temperature of the thermal fuse (FU1132) exceeds about 228 °C due to the abnormal tem-
perature rise of the fixing heater, the thermal fuse melts, thus power to the fixing heater is inter-
rupted.
d. Fixing unit failure detection
The CPU assesses a fixing unit failure under the conditions a) to g) indicated below and it per-
forms the following three procedures:
1. Cuts off power to the fixing heater by setting the FIXING HEATER DRIVE (FSRD) signal "L".
2. Sets the RELAY DRIVE (RLYD) signal "L" to turn OFF the relay (RL101).
3. Stops the main motor, scanner motor, and high-voltage power supply system immediately,
and then sets the printer an error state and notifies the failure to the interface controller.
a) The main thermistor does not exceed 50 °C within 1.47 seconds after the start of start-up
temperature control.
b) The main thermistor remains 230 °C or more continuously for 1.5 seconds during fixing
heater temperature control.
c) The temperature of the main thermistor is 100 °C or less continuously for 1.5 seconds dur-
ing normal temperature control. Or, the main thermistor remains 50 °C or less continuously
for 1.5 seconds during between-sheet temperature control.
d) The temperature of the main thermistor remains less than 20 °C continuously for 3 seconds
during fixing heater temperature control.
e) The main thermistor does not exceed 100 °C within 30 seconds after the start of start-up
temperature control.
f) The sub thermistor remains less than 20 °C continuously for 1.5 seconds during fixing
heater temperature control.
g) The temperature of the sub thermistor is 320 °C or more continuously for 3 seconds during
fixing heater temperature control.
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