Epson SQ-B50/2550 Technical Manual page 135

Solenoid,
Iron Core /"
To the cap
<Valve is open.>
Turn the
solenoid on.
It
Air
<Valve is shut.>
REV.-A
Figure 2-81. Valve movement
2.4.3.8 Valve Solenoid Driving Circuit
The valve solenoid driving circuit is shown in Figure 2-81. (Refer also to Location 6/I-J of the SEIMA
Board Circuit Diagram in the Appendix). When the solenoid draws (for valve opening), a rush current
first occurs, which then switches to a maintaining current. Transistor 03 normally switches wile 04
is turned on during discharge of the charge accumulated at C5. This discharge provides the rush current.
bl
pi I
I
17I
I
11
20
V 2
OV
O·
gs
Upper: 04 collector terminal
Lower: 03 collector terminal
Figure 2-82. Valve Solenoid Driving Waveform
2-67