Canon LBP-860 Service Manual page 68

Table 2-4
Notes: 1. If you print up to 25 envelopes
continuously during normal
temperature control, the target
temperature is held at 183°C. If
y o u p r i n t
envelopes continuously, the
temperature is held al 178°C.
2. Ii" the thermistor-detected tem-
perature is 50°C or less when
the power is switched ON, this
f o r m e d f o r 1 5 m i n u t e s t o
improve fixing.
The printer has the following three
protection functions to prevent incorrect
activation of the fixing roller:
voltage. If it is abnormal, the CPU
detects the fixing unit error. interrupts
the power to the fixing roller heater, and
reports it to the video controller.
the upper roller surface temperature
rises abnormally and the thermistor
voltage falls below about 1.0 V (230°C).
the safety circuil in the power supply
interrupts the power to the fixing roller
heater regardless of the CPU output.
the upper roller surface temperature
rises abnormally and the thermoswitch
temperature e x c e e d s 2 1 0 ° C . t h e
power to the fixing roller heater.
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m o r e t h a n 2 5
2. Fixing unit error detection
The CPU assumes a fixing unit error In the
following cases, and informs the video
E r r o r m e m o r y c a p a c i t o r (C202)
charging detection
CPU is 1.62 V or more (C202 is charged)
when the power is switched ON
Thermistor broken-wire detection
b.
If the upper roller temperature does not
reach 33°C within 22 seconds of the
F i x i n g r o l l e r h e a t e r b r o k e n - w i r e
detection
If the upper roller temperature does not
reach the standby temperature within
200 seconds of the fling roller heater
being turned ON
Broken-wire detection after the fixing
unit becomes ready
If the upper roller temperature reaches
140°C in the standby state or during
printing
Thermistor short detection
S U R F A C E T E M P E R A T U R E s i g n a l
When the CPU detects a fixing error, the
following are performed:
Switches the fling roller heater OFF.
Sets the output from pin 27 (P63] to
capacitor (C2021.
Sets the RELAY DRIVE signal [RLD) to
31
power supply, and interrupts the power
to the fixing roller heater.
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