Fuser Temperature Control - Oki OKIPAGE 10e Maintenance Manual

3.9

Fuser Temperature Control

For the temperature control by heater control, the variation in the resistance of the thermistor is
A/D converted in IC2 and the resultant digital value is read and transferred to the CPU. The CPU
turns on or off the HEATON-N signal according to the value of the signal received from IC2 to keep
the temperature at a constant level.
Immediately after the power is turned on, the thermistor is checked for shortcircuit and
breakdown. If the thermistor is shorted, the A/D converted value shows an abnormally high
temperature, so that the shortcircuit can be detected. If the breakdown of the thermistor occurs,
the A/D converted value shows the normal temperature. In this case, the thermistor breakdown
can be detected by the sequence shown at the end of this section. If the heater is overheated,
5V supply is turned off when the resistance of the thermistor is detected to be exceeding the
predetermined value.
Power Supply Board
Thermistor
TH1
5V
TH2
CN2
Heater
1
2
41266201TH Rev.1
IC2
27
Thermistor
Breakdown
Detector
Abnormally
Circuit
High
Temperature
Detection
PC1
Circuit
Main Control Board
CPU
HEATON-N
116
Power
Supply
Interface
20
ACIN
5V
IC11
1
0C
2
20 /