Oki B 4100 Maintenance Manual page 420

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Fuser unit temperature control

The heater in the fuser unit is controlled by the thermister, IOGA3 and CPU to keep the

heater roller surface within a prescribed temperature range. The CPU supervises the status

of the port PC0 periodically, turning HEATON signal on and off according to CPU of PC0

(A/D converter input section) status to exercise temperature control.

At power on time, the CPU switches the output signal THON from pin 65 (between high

and low states) to check for a blown or shorted thermister according to the status of the

THCHK signal.

A built-in thermostat in the fuser unit prevents the heater from being overheated in event of

failures in the thermister, or temperature control circuit, etc.

Figure A3.2.18 shows the fuser unit temperature control.

Note: Heater control

Temperature of the heater at the time of printing is 150 ˚C to 180 ˚C. This temperature is

maintained by controlling the on and off operation of heater according to the input of the

thermister converted into analogue-digital (A/D) values by the CPU.

40055101TH Rev.4

Figure A3.2.18 Fuser Unit Temperature Control

1VP/2VP (Power supply unit)

L101, R1, etc.

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