Epson LQ-300 - Impact Printer, Service Manual

Page: 52 / 119

Operating Principles
Service Manual
2.3.8 Paper
Feed Motor Driver Circuit
Figure 2-19 shows the paper feed motor driver circuit, an open-loop, constant-voltage drive with
1-2 phase excitation.
The ports (pins 7-lo) on the CPU are used to control the stepping motor. The pulse signal from the
controls four and the stepping motor. The motor is driven at six speeds, 300,500,
600, 1000, 1200, and 1300 pps, to correspond to the idling voltage, the paper handling condition,
and the volume of paper feeding.
CPU controls motor driving speed. At the holding time, the
voltage is changed VX V) into VL (+5 V) via Q6 by the gate array.
Gate
Array
143
I
CPU (ICI)
M l l
MIO
PF Motor Drive
Transistors
PF_A
P FA
‘
VL
Vx
Figure 2-19. Paper Feed Motor Driver Circuit Diagram
2.3.9 Driver Circuit
Figure 2-20 shows the driver circuit block diagram. Print data, already expanded into
image is split by the and transferred to the circuit in the gate array in the system.
Port (pin 66) of samples voltage of the +35 via the A/D converter. By
sampling the +35 line voltage and deterrninin g the length of the head drive signal, it is
possible to maintain the energy supplied to head at a constant level. If the voltage from the
+35 V line is HIGH, shortens output If the voltage from +35 line is LOW,
ICI lengthens the output pulse.
CPU
BUS
62
Gate Array
VP
QM1 -6
●
,
●
●
●
●
●
●
●
●
●
:
●
●
●
●
●
●
●
,
●
+5 VP
d
Figure 2-20. Driver Circuit Diagram
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