Epson LQ-2550 Technical Manual page 54

Figure 2-4 shows the printhead cooling mechanism.
The printhead has a built-in thermistor to protect the dot wire drive coils from the high printhead
temperatures (which can occur after many hours of continuous printing) which may burn or degrade
them. The printhead temperature detected by the thermistor is converted into a voltage signal and fed
back to the control circuit. This is used for printhead protection and, if the printhead temperature rises
to about 40°C, the HF motor (Refer to Table 2-3 for its specif ications.) is turned on to cool down the
Another thermistor is used to protect the HF motor drive circuit from abnormal heating of the HF motor.
Item
Type
Drive Voltage
Coil Resistance
Drive Frequency
Driving Method
Thermal sensor
Figure 2-4. Printhead Cooling Mechanism
Table 2-3. HF Motor Specifications
I
Description
Two-phase 6-pole PM type stepper '
motor
35 VDC
I 1600PPS
Constant voltage drive
Thermistor
Thermistor
I
I &
1 OYO
One-phase excitation
I
Built-in
2-7
Remarks