Canon iR1020 Series, Service Manual

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Chapter 8
8-5
F-8-3
8.3.2 Failure Detection
0013-1185
iR1020J / iR1024J / iR1020 / iR1024 / iR1024A / iR1024N / iR1024F / iR1024i / iR1024iF
The CPU on the DC controller PCB will identify a fault in the fixing assembly if any of the following conditions (a through d) occurs; as a result,
- it will cut the power to the fixing heater.
- it will cause the relay drive signal (RYLD) to go '1' to turn off the relay and, at the same time, will communicate the presence of a fault to the image processor PCB.
a. Detection of thtermistor short circuit (excessively high temperature)
This failure is detected when the main thermistor has continuously detected a temperature equal to or higher than 235 deg C for 1 second or longer during temper-
ature control.
This failure is detected when the sub-thermistor has continuously detected a temperature equal to or higher than 300 deg C for 0.15 second or longer during tem-
perature control.
b. Detection of open thermistor (excessively low temperature)
This failure is detected when the main thermistor has continuously detected a temperature lower than 20 deg C for 0.5 second or longer during temperature control.
This failure is detected when the sub thermistor has continuously detected a temperature lower than 35 deg C for 0.15 second or longer after the end of start up.
This failure is detected when the sub-thermistor cannot detect a temperature equal to or higher than 75deg C even if 2.29 to 20 seconds have lapsed since start of
power supply to the fixing heater.
c. Detection of Drive circuit failure (zero-cross error)
This failure is detected when the number (cycle) of zero-cross inputs that have been counted every second has been outside the range (45-65 Hz) twice.
d. Detection of startup failure
This failure is detected when the main thermistor has detected a temperature lower than 45 deg C 2.29 seconds after start of power supply to the fixing heater.
This failure is also detected when the main thermistor temperature is lower than 150 deg C and the rise in the main temperature per second is less than 12 deg C or
when the main thermistor temperature does not reach the target value 20 seconds later.
Relay
circuit
Fixing unit
P1
NF NF
ASIC
Zerocross circuit
Heater drive circuit
J14
-12 J103
-3 RLYD
FSRDRV -13 -2
J14
-14 J103
-1 ZEROX
Power supply PCB DC controller PCB
AC
DC
F1 F2 SW1
J113
GND
SUBTH
-4
-3
GND
MAINTH
-2
-1
+3.3V, +5V, +24V
Low-voltage power
supply circuit
J15
-1 -3
Fixing heater
high
temperature
error detection
TH1 TH2
-2
-1
RL1
H1
Heater trigger
circuit
J25
TP