Tally Dascom 7010, Maintenance Manual

Page: 42 / 255

2-2. Operation of Control Parts
2-26
(5) Head temperature sensor
The head temperature sensor is used to detect the temperature of the thermal head (Unit,
Head). This sensor is a thermistor incorporated in the thermal head. Since the resistance of
the thermistor changes according to the temperature change, the voltage at pin 7 (HDTMP) of
U1 (CPU) changes accordingly. The CPU senses the voltage at pin 7 to detect the head
temperature. According to the temperature of the thermal head, the CPU controls the width of
printing pulse that is used to heat the thermal elements, to keep the printing density constant.
Printing operation when the head temperature rises abnormally:
When the head temperature rises to 70
°
C (158
°
F), printing stops after printing the current label.
In this case, the ERROR LED blinks and the LCD displays "Alarm Head Hot" on the operation
panel. When the head temperature falls below 60
°
C (140
°
F), the ERROR LED stops blinking,
the LCD returns to the original display “On Line”, and printing resumes.
Printing operation when the head temperature is too lower:
When the head temperature is lower than -10
°
C (14
°
F), printing is inhibited, and the ERROR
LED blinks and the LCD displays "Error Head Cold" on the operation panel. Printing is not
possible until the temperature of the thermal head gets warm.
60 ° C
(140
°
F)
70
°
C
(158
°
F)
Printing
(Stop)
Printing
Printing
(Stops)
J3
Thermal Head
5-8, 21-25
+3.3V
19
R102
HDTMP
U1 CPU
ANI2
7
Thermal Head
Temp. Sensor
(Thermistor)
[Main PCB]
HDTMP
C64
20