Protection Against Abnormally High Temperature - Konica Minolta bizhub c10 Service Manual

17. Fusing section
17.3.3

Protection against abnormally high temperature

• The machine provides protection at three different stages to prevent abnormally high
temperature of the fusing Unit.
A. Soft protection
• If the thermistor detects a temperature exceeding a predetermined value, the malfunc-
tion code representing abnormally high temperature is displayed. At this time, the heater
lamp is turned OFF forcibly and the initiation of any new print cycle is prohibited (abnor-
mally high temperature detection control).
B. Hard protection
• If the CPU overruns and the output level of the CPU of the mechanical control board
becomes a HIGH or LOW level, and not a pulse output, and a predetermined tempera-
ture or higher is detected, a circuit within the mechanical control board turns OFF the
relay to shut down the power supply to the heater lamp.
C. Thermostat protection
• If neither the soft protection nor hard protection can detect an abnormally high tempera-
ture due to a defective thermistor or other reason, the thermostat operates at the speci-
fied temperature. This shuts down the power supply to the heater lamp, thus forcibly
turning it OFF.
Heater Lamp
Thermistor
Thermostat
Laser Safety Switch
Triac Circuit
Power Switch
66
Confidential – for internal use only, do not distribute
5V
Heating Roller
GND
Fusing PressureRoller
Watchdog Circuit
Theory of operation ver. 2.0 Nov. 2007
Mechanical Control Board
CPU
A/D
Hard Protection
Circuit
FUSER WDT
RESET
Heater Remote
ON/OFF
4139to2097e0