Kenwood TK-3140 Service Manual page 11

8. Power Supply Circuit
Battery +B is supplied via a 3A fuse from the battery terminal
connected to the TX-RX unit. After passing through the power
switch, power supply (SB) is applied to the three AVRs. IC5
supplies 5V (5M) to the control circuit, and IC9 supplies 5V
(5C) to common circuits. IC6 supplies to the TX circuit, the RX
circuit and common circuits of needless save mode. During
transmission, 5TC becomes Low and Q3 is turned ON to supply
5V (5T) to the TX circuit. During reception, 5RC becomes Low
and Q2 is turned ON to supply 5V (5R) to the RX Circuit.
The power supply voltage monitor IC (IC404) monitors power
supply voltage (SB). If the voltage falls (less than 5V), the VOUT
port goes "LOW" level, the CPU INT port also goes "LOW"
level, and the CPU stops.
F400
+B
RF power amp (Q103 and Q106)
SB D405
IC401
ON/OFF
VOL
IC404
IC403
CE
IC402
CE
Fig. 15 Power supply circuit
CIRCUIT DESCRIPTION
14
VCC
10
RESET
IC400
IC309
CPU
71
INT
5C
Q405
5T
5TC
Q404
5R
5RC
5CNS
TK-3140
11