Protective Function; Failure Detection - Canon mf6600 Series Service Manual

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Technical Overview > Fixing Unit System > Fixing Control Circuit > Failure Detection
The DC Controller monitors the FIXING TEMPERATURE (FSRTH) signal and sends the
FIXING HEATER CONTROL (FSRD) signal according to the detected temperature. The
Fixing Heater control circuit controls the Fixing Heater depending on the signal so that the
heater remains at the targeted temperature.
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Protective Function

The protective function detects an abnormal temperature rise in the Fixing Unit and interrupts
power supply to the Fixing Heater.
The following three protective components prevent an abnormal temperature rise of the
Fixing Heater:
•
DC Controller
Fixing Heater safety circuit
•
Thermoswitch
•
1) DC Controller
The DC Controller monitors the detected temperature of the thermistor. The DC
Controller
makes the FIXING HEATER CONTROL signal inactive and releases the relay to interrupt
power supply to the Fixing Heater under the following condition:
Thermistor: 240°C (464°F) or higher
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2) Fixing Heater safety circuit
The Fixing Heater safety circuit monitors the detected temperature of the thermistor.
The Fixing Heater safety circuit releases the relay control circuit to interrupt power
supply
to the Fixing Heater under the following condition:
Thermistor: 270°C (518°F) or higher
•
3) Thermoswitch
The contact of the thermoswitch is broken to interrupt power supply to the Fixing Heater
under the following condition:
Temperature fuse: 228°C (442.4°F) or higher
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2 Technical Overview > Fixing Unit System > Fixing Control Circuit > Failure Detection
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Failure Detection

The DC Controller determines a Fixing Unit failure, makes the FIXING HEATER CONTROL
signal inactive, releases the relay to interrupt power supply to the Fixing Heater and notifies
the formatter of a failure state when it encounters the following conditions:
1) Start-up failure
If the detected temperature of the thermistor is kept a specified degrees or higher for a
•
specified period of heater start-up during the wait period.
If the detected temperature of the thermistor is kept a specified degrees or lower for a
•
specified period under the heater temperature control during the print period.
If the detected temperature of the thermistor does not reach its targeted temperature within
•
a specified period under the heater temperature control during the initial rotation period.
2) Abnormal low temperature
If the detected temperature of the thermistor is kept a specified degrees or lower for a
•
specified period under the heater temperature control.
3) Abnormal high temperature
If the detected temperature of the main thermistor is kept a specified degrees or higher for
•
a specified period.
4) Drive circuit failure
If a specified frequency of the FREQUENCY signal is not detected within a specified period
•
after the printer is turned on.
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