1) The CPU monitors the thermistor (TH1) voltage. If the thermistor (TH1) voltage is abnormal, the CPU judges that the fixing heater is faulty and turns off the

relay (RL1). At the same time, the CPU notifies the DC controller of occurrence of the fixing heater failure.

2) If the temperature of the fixing heater rises abnormally and the thermistor (TH1) detects a voltage lower than about 0.7 V (equivalent of 240 deg C), the fixing

heater high temperature detection circuit cuts off the power supplied to the fixing heater.

3) If the temperature of the fixing heater rises abnormally and the thermo switch (TP1) detects a temperature higher than 244 deg C, the thermo switch turns off to

cuts off the power supplied to the fixing heater.

Failure Detection

The CPU performs error detection at intervals of 40 msec. If any one of the cases a to d occurs, the CPU stops the machine completely. To restart the machine,

remove the cause of the failure and carry out initial rotation. If a failure is detected, an error code "EXXX-YYYY" (XXX stands for an error code and YYYY stands

for a detail code) is displayed on the operation panel.

a. Failure at startup

1) The main thermistor has detected temperatures lower than 30 deg C continuously for 400 or more msec since 1 second lapsed after energization of the fixing

heater.

2) The main thermistor has detected temperatures lower than 70 deg C continuously for 400 or more msec since 2 seconds lapsed after energization of the fixing

heater.

3) The sub-thermistor has detected temperatures lower than 75 deg C continuously for 400 or more msec since 5 seconds lapsed after energization of the fixing

heater.

4) The temperature rise detected by the main thermistor is less than 5 deg C when energization of the fixing heater starts, when the temperature detected by the main

thermistor is less than 100 deg C, or when 1 sec has lapsed since start of energization.

5) The main thermistor has detected temperatures less than 115 deg C continuously for 400 or more msec since 1 second has lapsed after detection of 100 deg C.

6) The main thermistor has detected temperatures less than 150 deg C continuously for 400 or more msec since 1 second has lapsed after detection of 140 deg C.

7) The main thermistor has detected temperatures less than 165 deg C continuously for 400 or more msec since 1 second has lapsed after detection of 160 deg C.

8) The target printing temperature is not reached when 30 seconds have lapsed since start of the initial rotation.

b. Low temperature detection during temperature control

During temperature control, the main or sub thermistor has detected low temperatures continuously for 400 or more msec after the target temperature was reached.

c. Abnormally high temperature detection

1) The main thermistor has detected 240 C deg irrespective of whether the fixing heater is of or off.

2) The sub thermistor has detected 295 deg C irrespective of whether the fixing heater is of or off.

3) An abnormally high temperature has been detected in the ASIC irrespective of whether the fixing heater is of or off.

d. Drive circuit failure

1) The zero crossing signal frequency of the power supply has not been detected during initial rotation.

2) During temperature control, no zero crossing signal has been input for 3 seconds.

3) A triac short circuit has been detected in the ASIC.

Fixing System Error Codes

E000-0000 STARTUP ERROR

The temperature detected by the main and sub thermistors did not reach the prescribed temperature during startup control.

E001-0000 ABNORMALLY HIGH TEMPERATURE (detected by main thermistor)