Canon PC920 Service Manual page 172

CHAPTER 6 FIXING SYSTEM
6. Protective Functions
The machine is equipped with the following protective functions to prevent malfunction of the
fixing heater.
a. Thermistor (TH1)
The microprocessor on the DC controller PCB monitors the voltage of the thermistor (TH1); if
an abnormally high or low temperature is detected, the microprocessor sends the fixing heater error
signal (HEAT_ERR*) to the timer circuit and, at the same time, indicate an error code (E000
through E003).
In response, the timer circuit sends the relay drive signal (RLOFF*) to the auxiliary power
supply in about 1.2 sec after it hs received the fixing heater error signal (HEAT_ERR*).
The auxiliary power supply turns off the relay (RL601) to turn off the power. Then, the data of
'E0' (associated with the heater) is retained so as to indicate 'E0' when the power is turned on the
next time.
'E0' is backed up for about 5 min. After 'E000' through 'E003' is indicated in the control panel
and the power is turned off, the machine will indicate 'E0' in the control panel if the power switch
is turned on within 5 min, not recognizing a press on the Copy Start key. If the Copy Start key is
pressed after about 5 min, however, a press on the Copy Start key will be recognized.
If an error is detected in relation to the heater during copying operation, the machine will
indicate 'E000' through 'E003' in the control panel once again and turn off the power.
Related Error Code
E000
• The temperature detected by the thermistor (TH1) is not 65°C in 1.5 sec after the Copy
Start key is pressed.
• The temperature detected by the thermistor (TH1) is not 150°C in 4 sec after the Copy
Start key is pressed.
E001
• The temperature detected by the thermistor (TH1) is 230°C or more.
• The temperature detected by the thermistor (TH1) is higher than the control temperature
by 30°C or more.
• The thermistor (TH1) has detected an increase in temperature of 100°C or more in 1 sec.
• The thermistor (TH1) has detected an increase in temperature of 40°C or more after it
detected 100°C in standby state.
• E0 detection signal (E0_DT) has been detected twice in succession.
E002
The temperature detected by the thermistor (TH1) is 150°C or higher and, thereafter, maxi-
mum power has been supplied to the fixing heater for 10 to 14 sec during copying operation.
E003
The temperature detected by the thermistor (TH1) is 160°C and then 150°C or lower during
copying operation.
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COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)