Citizen CL-E720DT Technical Manual page 36

Chapter 2 Operating Principles
2-2.
Operation of Control Parts
Abnormally high temperature detection:
To protect the "SA PF Motor" from being damaged, an abnormally high temperature detection
circuit is provided. If the temperature of the "SA PF Motor" exceeds a set temperature limit, the
LED on the operation panel blinks in red and the LCD displays "Error System Fail", and the
printer goes off-line. To recover from the error status, turn OFF the printer once and then turn it
ON.
A reference voltage, i.e., an allowable temperature limit, is applied to pin 6 of the comparator
(U7B), while the sensor output voltage (TMPPF) from the PF motor temperature sensor is
applied to pin 5.
If the temperature of the "SA PF Motor" exceeds a certain level, the PF motor temperature
sensor output voltage becomes lower than the reference voltage, and the pin 7 of U7B goes to
"Low" level. At this time, pin K1 (nTMPERR) is "Low" and the FPGA (U5) detects an abnormally
high temperature.
In this abnormal state, the printer stops +24V DC supply to the "SA PF Motor". Also, it stops
+24V DC supply to the "SA Head".
CL-E720DT
2-22