Supervision Circuit For The Thermal Head Temperature - Panasonic KX-FM89BX Service Manual

6.3.9. SUPERVISION CIRCUIT FOR THE THERMAL HEAD TEMPERATURE

1. Function
The thermistor changes the resistor according to the temperature
and uses the thermistor's characteristics. The output of pin 169 of
IC501 becomes a low level. Then when it becomes a high level, it
triggers point A. In point C, according to the voltage output time,
the thermal head's temperature is detected.
After the thermal head temperature is converted to voltage in B, it is then changed to digital data
in the A/D converter inside IC501. The CPU decides the strobe width of the thermal head
according to this value. Therefore, this circuit can keep the thermal head at an even temperature
in order to stabilize the printing density and prevent the head from being overheated.
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