Epson PX-8 Technical Manual page 168

REV.-A
3.2.5 Power Supply Circuit
The RAM disk unit power supply circuit consists of a +4.8V, 450 mAH rechargeable battery, a
charge circuit, a logic voltage source circuit, and a backup circuit.
1. Rechargeable battery and charge circuit
The battery is connected to the MAP-RF board via a connector CN 2. The switch (SW2) on the
board allows the user to connect or disconnect the battery to the MAP-RF board.
The circuit surrounding the battery is shown below.
1) Battery backup switch SW2
This switch should be reset OFF when stor-
ing this unit alone or when not using it for a
long period of time as attached to the Main
Frame. With this switch reset OFF, the bat-
tery is prevented from any discharge other
than the natural one so that the longest life
can be ensured.
*
The backup line circuit operates irrespective
of the setting of this switch; when the switch
is reset OFF, the line is backed up from the
Main Frame battery and its working time
may be shortened.
2) Battery charging
The battery is always charged toward the full
via either of the following two charging
paths:
When the Main Frame AC adaptor is con-
nected to the AC power source.
V
CH
-->
D2
-->
R1
-->
SW2
-->
CN2
-->
Battery
When the AC adaptor is not used but the bat-
tery voltage is lower than the VB 1 supply vol-
tage from the Main Frame.
V
B1
-->
D3
-->
R2
-->
SW2
-->
CN2
-->
Battery
3-22
NI-CD 12V450mAh
r-11-
----I
b
eN 2
SW2
(I
+ -
r---------+-------------~BACKUP
v
C
H
v
B
R37 33 K
LOGIC
\tc
IS2075K
x3
D9
C945
V
L
LINE
Fig. 3-32 Power Supply Circuit