Epson LX-300, Service Manual

Page: 46 / 107

Operating Principles
Service Manual
2.3.7 Paper Feed Motor Driver Circuit
Figure 2-18 shows the paper feed motor driver circuit, open-100P, drive with
1-2 phase excitation.
The ports (pins 137-
140)
on the system (ICI) are to stepping motor. pulse
signal
from the
controls four transistors and the stepping motor. motor is driven at fiv
e
speeds, 800, 900, 1000, 1200, 1300 to correspond to voltage and the paper
condition. The controls motor speed. At voltage is
into VL
via
A4 by the “
SYSTEM (ICI)
MOTOR
Q 1 1
PFA
-
’
3 7
13s
Q 1 3
I
‘ L
VP
Figure 2-18. Paper Feed Motor Driver Circuit Diagram
2.3.8 Driver Circuit
Figure 2-19 shows the driver block diagram. Print data, already expanded into
image data, is split by the CPU block and transferred to the latch in the gate array block in
the system (ICI). Port AN6 (pin 66) of ICI samples the voltage of the +35 line via the A/D
converter. By sampling the +35 line voltage and dete
the length of the head drive
signal, it is possible to maintain the energy supplied to the head at a constant level. If the voltage
from the line is HIGH, ICI shortens the output pulse. If the voltage from the +35 line is
LOW, ICI lengthens the output pulse.
SYSTEM (ICI)
I
R
IO
D1
- c ?
R l l
Figure 2-19. Driver Circuit Diagram
(
(
2-16