Epson PX-8 Technical Manual page 49

REV.-A
The diode, inserted across the signal line and ground, clamps the signal to the ground level. eli-
minating the negative component. While the positive component is fed back to the auxiliary bat-
tery via the other diode D14.
Sub CPU
7508
P70
--k1f---~
P42
R48
47K
R6
220
...--___ V8
Return voltage
from LCD
o - - - - - - - - 1 - - - - - - - - - - - - - - - -........
-----4H~
III
regulator
J
'"'11 I I -
Auxiliary battery
~---~~~~~ ........ -~ Q20
"-------'_ VB
20K
Fig. 2-19 Feedback Circuit
Fig. 2-19 is the feedback circuit redrawn for clarification. This circuit provides the charging path
to the auxiliary battery while power is on.
7508, P70
(Power control)
7508, P42
(Main/auxiliary
battery switching)
Feedback voltage
waveform as
observed
Power off
• ..------Auxiliary battery change----------'~~
1 - - - - - - - . . 1
Fig. 2-20 Major Voltages of LCD Drive Power Regulator Circuit
2-25