4-11
UP-895/(E)
4-4-7. Monitor of Head Temperature Sensor
The change in the resistance value of the thermistor inside a thermal head is converted into a voltage
using a head temperature detector circuit (IC401) and read by a system control (IC304). The voltage
value is converted from analog to digital. Density (gamma) correction, fan motor control for head
cooling, and head-in cleaning discrimination are performed according to the digital value.
4-4-8. Control of Head Fan Motor (for Head Cooling)
The head fan motor is operated when a system control (IC304) controls driving transistors (Q400 and
Q403). The head fan motor is turned on when the head temperature is more than approximately 50 dC or
during printing.
Operation of head fan motor
IC304-26 pin Operation
L OFF
HON
4-4-9. Control of Video Circuit Section
A system control (IC304) controls the video circuit section as shown in the table below.
IC304 I/O Function
77pin O Switches THRUE and EE signals. L: ON
H: OFF
59pin O Sets the trap filter to ON or OFF. L: ON
H: OFF
60pin O Selects NTSC or PAL. L: When an NTSC signal is input
H: When a PAL signal is input
53pin O Sets the AGC function to ON or OFF. L: ON
H: OFF
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