Paper Feed Motordrivecircuit; Printhead Drive Circuit - Epson LQ-300 Service Manual

Operating Principles
Feed Motor Driver Circuit
2.3.8 Paper
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
600, 1000, 1200, and 1300 pps, to correspond to the idling voltage, the paper handling condition,
and the volume of paper feeding. The CPU controls motor driving speed. At the holding time, the
Gate
Figure 2-19. Paper Feed Motor Driver Circuit Diagram
2.3.9 Printhead Driver Circuit
Figure 2-20 shows the printhead driver circuit block diagram. Print data, already expanded into
image data is split by the CPU and transferred to the latch circuit in the gate array in the system.
Port AN6 (pin 66) of IC1 samples the voltage of the +35 VDC line via the A/D converter. By
sampling the +35 VDC line voltage and deterrninin g 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
+35 V line is HIGH, ICI shortens the output puke. If the voltage from the +35 VDC line is LOW,
ICI lengthens the output pulse.
CPU
BUS
62
Figure 2-20. Printhead Driver Circuit Diagram
2-16
CPU (ICI)
Array
Mll
MIO
143
I
Gate Array
QM1 -6
+5 v VP
d
PF Motor Drive
Transistors
PF_A
P FA
'
VL
Vx
VP
,
:
,
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