Epson Stylus 1500, Service Manual

Page: 60 / 185

Reset Circuits
The C172 MAIN board contains two monitor reset circuits: +5 V and +42 V. The +5 V circuit
monitors the voltage level of the +5 V line (logic line) using a PST592D reset IC (IC9), and outputs a
reset signal to the CPU (IC1) and the E05E16 gate array (IC2) when the voltage level drops below
+4.0 V. The +42 V circuit monitors the voltage level of the +42 V line using an M51955B reset IC
(IC8), and outputs a reset signal to the CPU when the voltage level drops below +33.3 V. This
causes a non-maskable interrupt (NMI).
Sensor Circuits
The following sensor circuits enable the C172 MAIN board to monitor printer mechanism status:
+42 V
+5 V
NMI
P84
CPU ( IC1 )
+5 V
PST592D
(IC9)
E05B16 (IC2)
RESET
XRESET
201
30
1
6 10
15
M51955B
(IC8)
3
2
Figure 2-21. Reset Circuit Block Diagram
THS
1 3
+ 5 V
A N 0
20
(CN 7 )
CPU (IC1)
1
2
1
2
3
1 0
9
2
5
45
P7 1
P 7 0
H P
+5 V
(CN10)
(CN 9 )
P 7 4
1
6
B H C O
(CN13)
3
+5 V
(CN12)
+5 V
1
P 7 2
Re a r PE
Se nso r
+5 V
(CN11)
4
+5 V
P E
P E
( CN8 ) C H C O
P 7 7
9
1 3
+ 5 V
+5 V
2
2
B K E N D
P7 3
5
P 7 6
1
8
R E L E A S E
(CN14)
+ 5 V
2
1
2
P 8 3
D E
+5 V
(CN15)
1 4
+5 V
Thermistor
Color Ink Cartridge (Option) Sensor
Black Ink End Sensor
Black Ink Cartridge Sensor
Fro nt PE
Sen sor
HP Sensor
Disengage
Se nso r
Release Sensor
Figure 2-22. Sensor Circuit Block Diagram
Operating Principles
EPSON Stylus 1500 Service Manual 2-19