2.3.2 System Reset Circuit
Control circuits IC1 and IC2 are initialized when a RESET signal (LOW level) is output from port 1 (VOUT)
of IC10. IC10 monitors the +5 V line on port 3, and resets under the following conditions:
1.
When the power supply is turned on, a RESET signal is output. RESET is canceled when the
+5 V line goes up to 4.2 V, and then 100 ms passes.
2. When the +5 V line goes below +4.2 V, a RESET signal is output. RESET is canceled when the
+5 V line goes back up to 4.2 V and then 100 ms passes.
2.3.3 Printhead Driver Circuit
The standard voltage for the A/D converter is made in ZD1 and input to CPU port 78. Based on this standard
voltage, the A/D converter in the CPU operates. Port 74 monitors the +35 V line between R50 and R51 to
determine the printhead driver pulse width. Using the monitored voltage, the CPU converts the voltage to a
digital value and decides the printhead driver pulse width, and then transports the data to the gate array via
CPU port 15. Based on the monitored voltage, the CPU decides the printing interval. Port 73 monitors the
printhead temperature to protect the printhead. If the temperature exceeds 95° C (213° F) , printing is
stopped.
1
2
3
4
5
VCC (+5V line)
VOUT (RESET)
RESET
RESET
Power On
(v)
100ms
100ms
Figure 2-33 Reset Signal Output Timing
V O U T
M R E S
V C C
G N D
+ 5 V
+ 5 V
R 4 7
1 K
IC1 0
P S T5 9 2 0
C 1 6
0 .1 U
I C 1
IC2
TP M 9 6 C0 4 1 A F
2 3 RESET
6 1
R E S E T
1
2
3
4
E05B24YA
Figure 2-32 Reset Circuite
C P U
G a t e
A r r a y
C 1 9
ZD 1
+ 3 5 V
7 8
7 9
7 4
7 3
R 5 1
R 5 0
+ 3 5 V
R 4 9
A d d r e s s
D at a Li n e
3 7
4 4
~
2 8
~
2 1
Pr in thead Dr ive Sign al
6 9 7 6~ 89 91 ~9 9
Printhead Drive Transistor Q1~ Q12, Q13~24
Print Head
H T M P
+
C 9
+ 3 5 V
+ 3 5 V
3 1
1 5
Figure 2-34 Printhead Drive Circuit
Operation Principles
LQ-2070 Servcie Manual
2-24
Rev.A
Summary of Contents for 2070 - LQ B/W Dot-matrix Printer
Page 1: ...EPSON TERMINAL PRINTER LQ 2070 SERVICE MANUAL EPSON 4006244 ...
Page 5: ...REVISION SHEET Revision Issued Date Revision Page Rev A April 8 1996 1st issued ...
Page 11: ...Product Description LQ 2070 Service Manual Figure 1 1 Exterior View of the LQ 2070 1 2 Rev A ...
Page 55: ...LQ 2070 Service Manual Operating Principles Rev A 2 7 ...
Page 58: ...Operation Principles LQ 2070 Servcie Manual 2 10 Rev A ...
Page 63: ...Down LQ 2070 Service Manual Operating Principles Rev A 2 15 ...
Page 112: ...Disassembly and Assembly LQ 2070 Service Manual 3 34 Rev A ...
Page 146: ...Maintenance LQ 2070 Service Manual 6 4 Rev A ...
Page 165: ...EPSON ...