Epson Stylus Color 740 Service Manual

EPSON Stylus COLOR 440, 640, and 740 Chapter 2 Operating Principles
58
Power-Off Timer Circuit
The timer IC measures how lon
g
the printer is turned off. When the
printer is turned on, the IC sends the power-off time to the
g
ate arra
y
.
The power-off time determines how extensivel
y
the printhead is cleaned
at power-on.
In the St
y
lus COLOR 440 and 640, an external cr
y
stal oscillator
(
CR1 or
CR3
)
provides the basic timin
g
pulse. In the St
y
lus COLOR 740, the
oscillator is built into IC8, the same chip that contains the reset circuit.
Since the cr
y
stal’s oscillation produces an analo
g
waveform, the timer
IC converts it into a s
q
uare wave to enable it to be processed di
g
itall
y
.
When the printer is on, power is supplied to the timer throu
g
h the 5-volt
power bus. When the printer is turned off, a 3-volt lithium batter
y
powers the chip. Diodes on the power suppl
y
line prevent the batter
y
from char
g
in
g
when the printer is on, and from dischar
g
in
g
back into the
power line when the printer is off.
Figure 2-26. Timer Control Circuit for Stylus COLOR 440
Figure 2-27. Timer Counter Circuit for Stylus COLOR 640
Figure 2-28. Timer Counter Circuit for Stylus COLOR 740
+5
Batt1
D7
D1
C4
0.1u
S-3510ANF
(IC5)
XI
XO
2
3
VCC
GND
8
4
5
6
7
123
121
124
CR1
E05B44
(IC2)
TCE
TCLK
TDATA
RM7
CS
/SCK
/SIO
+5
Batt1
D1
D4
C4
0.1u
S-3510ANF
(IC10)
XI
XO
2
3
VCC
GND
8
4
5
6
7
125
123
126
CR3
E05B43
(IC2)
TCE
TCLK
TDATA
RM7
CS
/SCK
/SIO
RTC-9810
(IC 8 )
Vin
9
7
8
5
6
4
CE
SCLK
Data
Vdd
Vbk
GND
20
21
23
E05B 588
(IC 2 )
T M C S
T M C K
TM D ATA
+5
14
Batt1

Epson Stylus Color 740 Specifications

General

Brand	Epson
Model	Stylus Color 740
Category	Printer
Language	English