Reset Circuits; Sensor Circuits - Epson Stylus 1500 Service Manual

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).
Figure 2-21. Reset Circuit Block Diagram

Sensor Circuits

The following sensor circuits enable the C172 MAIN board to monitor printer mechanism status:
Rear PE
1
P E
Sensor
2
(CN11)
Front PE
1
P E
Sensor
2
(CN10)
1
HP Sensor H P
2
3
(CN9 )
Disengage
1
Sensor D E
2
(CN15)
Figure 2-22. Sensor Circuit Block Diagram
EPSON Stylus 1500 Service Manual
+42 V
M51955B
2
6 10
(IC8)
15
+5 V
+5 V 30
201
PST592D
3
1
(IC9)
CPU (IC1)
+5 V
20
4
A N 0
P 7 2
+5 V
9
P 7 7
+5 V
+5 V
3
P7 1
P7 3 5
+5 V
45
2
P 7 0
6
P 7 4
+5 V
1 4 8
P 7 6
P 8 3
+5 V
Operating Principles
CPU (IC1)
NMI
P84
RESET
E05B16 (IC2)
XRESET
+5 V
Thermistor
1 3
(CN7 )
THS
+5 V
Color Ink Cartridge (Option) Sensor
1 3
(CN8 )
C H C O
1 0
Black Ink End Sensor
B K E N D
9
(CN12)
5
+5 V
1
Black Ink Cartridge Sensor
B H C O (CN13)
2
+5 V
1
Release Sensor
RE L E A S E
2 (CN14)
2-19