Epson Stylus 1500 - Reset Circuits; Sensor Circuits

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
610
15
M51955B
(IC8)
3
2
Figure 2-21. Reset Circuit Block Diagram
THS
13
+5 V
AN0
20
(CN7)
CPU (IC1)
1
2
1
2
3
10
9
2
5
45
P71
P70
HP
+5 V
(CN10)
(CN9)
P74
1
6
BHCO
(CN13)
3
+5 V
(CN12)
+5 V
1
P72
Rear PE
Sensor
+5 V
(CN11)
4
+5 V
PE
PE
(CN8)
CHCO
P77
9
13
+5 V
+5 V
2
2
BKEND
P73
5
P76
1
8
RELEASE
(CN14)
+5 V
2
1
2
P83
DE
+5 V
(CN15)
14
+5 V
Thermistor
Color Ink Cartridge (Option) Sensor
Black Ink End Sensor
Black Ink Cartridge Sensor
Front PE
Sensor
HP Sensor
Disengage
Sensor
Release Sensor
Figure 2-22. Sensor Circuit Block Diagram
Operating Principles
EPSON Stylus 1500 Service Manual 2-19