Canon LASER CLASS 730i Service Manual page 58

4.4.1 Fixing heater Malfunction
The printer controller on the ECU board detects a fixing heater malfunction in the following
instances.
1. Abnormally high-temperature main thermistor (all modes)
The CPU assesses an abnormally high temperature when it detects a
temperature of 245°C or more for 1 second continuously.
2. Abnormal warm-up 1 (initial temperature control mode)
The CPU assesses an abnormal warm-up 1 if the detected temperature is lower than 120°C
for 1 second continuously after the heater has been energized for 20 second.
3. Abnormal warm-up 2 (initial / print temperature control mode)
It the reading of the main thermistor does not exceed a specific level of temperature within
75 sec after the fixing heater is supplid with power, the CPU will identify the condition as
being abnormal warm-up2.
4. Low temperature during temperature control (print / between-page
/ postprint temperature control mode)
The CPU assesses a low temperature during temperature control when the detected
temperature is lower than 120°C for 1 second continuously in the print / between-page /
postprint temperature control mode.
5. Initial broken main thermistor wire (initial temperature control mode)
The CPU assesses an initial broken main thermistor wire when the output voltage from the
main thermistor is about 3.3V (line voltage of 3.4V) or more for 1 second continuously.
6. Broken main thermistor wire (print / between-page / postprint temperature
control mode)
The CPU assesses a broken main thermistor wire when the output voltage (FSRTH) from
the main thermistor is about 3.3V (line voltage of 3.4V) or more for 0.5 second
continuously.
7. Abnormally high-temperature sub thermistor (all modes)
The CPU assesses an abnormally high temperature sub thermistor when it detects the
temperature of the sub thermistor is 315°C or more for 1 second continuously.
8. Abnormally low-temperature sub thermistor (initial / print control mode)
The CPU assesses an abnormally low temperature sub thermistor when it detects the
temperature of the sub thermistor is less than 75°C for 2 seconds continuously after the
heater has been energized for 20 seconds.
9. Abnormally low-temperature sub thermistor 2 (heater OFF mode)
The CPU assesses an abnormally low temperature sub thermistor 2 when all of the
following conditions are met while the heater is OFF at the print completion:
• Ready.
• Print is not cancelled.
• After the completion of the initial control mode.
• Before the trailing edge of print paper passes through the delivery sensor,
the temperature of the sub thermistor is less than 75°C.
• Immediately before the heater is OFF, the temperature of the sub thermistor
is less than 75°C.
LASER CLASS 730i/720i/710 Chapter 2: Technical Reference
2-17
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