STYLUS 800 Service Manual Operating Principles
2.3.2.1 Reset Circuits
The
C106
MAIN BOARD contains two reset circuits: the +5 V monitor reset circuit and the +35 V
monitor reset circuit. The +5 V monitor reset circuit monitors the voltage level of the +5 V line,
using reset
IC
PST592
(IC12),
and outputs a reset signal to both the CPU (ICI,
TMP96C141)
and the
E05A85EB
gate array
(IC3),
when the voltage level drops below +4.2 V. The +35 V monitor reset
circuit, on the other hand, monitors the voltage level of the
+35V
line, using reset
IC
51955BFP
(IC1l), and outputs a reset signal to the CPU. The reset signal is generated when the voltage level
drops below +28 V, and this causes a non-maskable interrupt
(NMI).
+5VDC
+3SVDC
&&
237
RESET
E05A85EB
(IC3)
7
I_-EL.J
Figure 2-14. Reset Circuit Block Diagram
2.3.2.2 Sensor Circuits
The following sensor circuits enable the main board to monitor printer mechanism status:
1) HP sensor
2) PE sensor
3)
IE
sensor
4)
Thermistor
A photocoupler-type HP (home position) sensor is attached to the back of the
carriage unit to detect the carriage home position as a print reference position. A
HIGH level from the signal indicates that the carriage is in home position.
A mechanical switch PE (paper end) sensor is built into the printer mechanism to
determine whether there is paper in the printer or not.
Two electrical contacts are attached to the ink cartridge holder in the carriage unit,
and when the ink cartridge is installed, the metal pins built into the ink cartridge
touch these contacts. The
IE
(ink end) sensor circuit applies a HIGH level signal
when
performin
g the ink end status detection operation. The ink level is
determined by the resistance between the two contacts by measuring the input
signal level with analog port ANO (pin 73) of CPU.
A thermistor is attached to the
printhead
unit to monitor its temperature. The CPU
changes the
printhead
drive signal’s pulse width (charge pulse width) based on the
temperature level.
PE
+5V +5V +5V
(CN4)
P
10 I
x
JJ
r
k)
+5V
980
slve
w
m
Ink
IC9
cartlt@l?
E05A85E9
INK
~
“1
(IC3)
i
..~:~
i
,.
Cl=u
‘+”
‘
,,,
.
L.—.
J
(lCl)
+5V
I
Figure 2-15. Sensor Circuit Block Diagram
Rev. A
2-13