Pump Motor Drive Circuit - Epson SQ-1170 Service Manual

Figure 2-47 shows the timing for discharge/charge pulse.
(2) Printhead Voltage Supply Circuit
The viscosity of ink is subject to change due to the temperature. If the viscosity is too high, ink injection
becomes difficult. To eliminate this difficulty, the head drive voltage (Vh: the +35 VDC voltage boosted
to 83 -123.7 VDC in this circuit) is controlled based on the ink temperature detected by the thermistor.
That is, the temperature is fed back to the voltage supply circuit and controlled by TL494.
Since each printhead produced shows slightly different characteristics, this difference must be
neutralized by adjusting the head drive voltage. For this purpose, several zener diodes (used for
detecting output voltage) and a DIC jumper are provided. When the printhead or the MAIN board is
replaced, adjust the DIC jumper to connect the zener diodes in proper arrangement.
For safety, this circuit is

2.3.7 Pump Motor Drive Circuit

Figure 2-48 shows the block diagram of the pump motor drive circuit.
A DC motor is used to drive the pump. The drive circuit is controlled by the collector-follower
bridge - SOH03 (IC 16).
The rotational direction of the motor is controlled through the ports on E05A65. If PMCW signal is
transmitted from PCO, the motor rotates CW. If PMCCW signal is transmitted from PC 1, the motor rotates
Ccw.
CPU
Bus
Figure 248. Block Diagram of Pump Motor Drive Circuit
Figure 247. Timing for Discharge/Charge
disconnected when a case open condition is detected.
P c l
2-36
Pulse
I
PM+
NPN2B
I
I
I
Pump
MOTOR