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Power Supply/Power Control Circuitry
TO: N-20
MAIN PCB
JP18
GO_SW
1
2
CHECK BATTERY
TP88
TEST
SW1
S2
MEASURE
BUTTON
Figure 9-24: User Controls Circuit
Power supply circuitry is located on the auxiliary PCB and consists of the
following subsections:
•
Batteries — Four 1.5-V alkaline "C" size batteries provide 4–6 VDC power.
•
Power control circuitry — Power control circuitry is connected to the
batteries. It senses any press of the On/Off button and switches on the power
supplies. Reverse current limiting protects the N-20PA from damage if
batteries are inserted incorrectly.
L11
VCC
L12
R74
1K
C126
100PF
R80
221
Technical Supplement
VCC
TP72
R102
TEST
15K
VCON
GO_BTN
R78
150K
R79
3.32K
C66
.01UF
TP71
C123
TEST
100PF
R71
150K
TP81
BAT_BTN
TEST
C64
.01UF
TO: N-20
AUX PCB
JP8
GO_SW
1
2
GO BTN
To U21
pin 4
9-23
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