Canon MultiPASS C5000 Service Manual page 69

5.5.3
Heat protection mechanism
The BJ cartridge head's aluminum panel becomes hot during printing. It also gets hot if
printing continues even after the ink in the cartridge has been depleted. The aluminum
panel's temperature is detected by the BJ cartridge's head temperature sensor.
When the carriage is to be moved to the cartrldge replacement position, the following
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applies:
If the detected temperature exceeds 5O"C, "WAIT COOLING" is displayed and the
carriage does not move. This is to prevent the user from touching the BJ cartridge's
aluminum panel. After several minutes when the temperature decreases, the cartridge
replacement procedure must be executed again.
When a temperature exceeding the standard temperature is detected, the following
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applies:
During printing, the printing head temperature is monitored every 50 ms. If the
printing head temperature exceeds 75"C, a 3.5.second wait period is inserted after each
printed line for 20 seconds. This is to allow the printing head to cool. After 20 seconds,
the head temperature is checked. If the temperature has dropped below 75"C!, normal
printing resumes without any wait period inserted. However, if the head temperature is
still above 75"C, the wait period is inserted after each printed line until the printing
head cools suffXently.
If a head temperature exceeding 100°C is detected for 0.2 sec. during printing, it will be
displayed. The printing operation will also stop.
If a head temperature exceeding 100°C is detected for 1 sec. during printing, it will be
deemed as a BJ head temperature sensor error and "CHECK PRINTER ##337" will be
displayed. The printing operation will also stop.
5.5.4 Overcurrent protection
The fax unit has an overcurrent protection circuit with n built-in fuse to prevent an
abnormal tcmpcrature increase if an ova-current flows to the motors and power supply due
to a driver IC problem, software lockup, or short circuiting.
Protected Component
Document feed motor
Paper feed motor
Carriage motor
Power supply unit
Safety Device
IC protector lFIJ3) on PCNT board
IC protector rFU1) on PCNT board
IC protector tFU21 on PCNT board
Glass-tube current fuse (125V, 4A), overcurrcnt protection
circuit
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Chapter 7: General Description