Reset Circuits; Sensor Circuits - Epson STYLUS 4001968 Service Manual

STYLUS 800 Service Manual

Reset Circuits

2.3.2.1
The MAIN BOARD contains two reset circuits: the +5 V monitor reset circuit and the +35 V
C106
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
circuit, on the other hand, monitors the voltage level of the +35V line, using reset IC 51955BFP
drops below +28 V, and this causes a non-maskable interrupt (NMI).
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 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.
2) PE sensor A mechanical switch PE (paper end) sensor is built into the printer mechanism to
determine whether there is paper in the printer or not.
3) IE sensor 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.
4) Thermistor
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
Figure 2-15. Sensor Circuit Block Diagram
Rev. A
RESET
9
INK ~
(lCl)
Operating Principles
10 I
Ink
.
I
"1
'
2-13