Circuit Description - Kenwood TK-5810H Service Manual

1-1. Final Amplifier Circuit (From Power module to
Antenna output): TK-5810H (B)
The transmit signal from the TX terminal (CN1) of the final
unit (X45-380) is amplified by the power module (IC1).
The signal amplified by the power module is divided into
two signal, and further is amplified by the final amplifier
(Q1,Q2). The each signal from Q1 and Q2 is combined.
The combined signal passes through the antenna switch
(D5, D6, D7, D8, D15, D16), CM coupler and low-pass filter,
then it is fed to the antenna.
CM coupler is a line for detecting forward wave and
reflected wave.
FINAL UNIT (X45-380)
+B
IC1
POWER
TX(CN1)
MODULE
1-2. Temperature Protection Circuit : TK-5810H (B)
To prevent thermal destruction of the power module
(IC1) and final amplifier (Q1,Q2), this circuit reduces APC
voltage when temperature of the power module (IC1) and
final amplifier (Q1,Q2) rises.
The CPU (IC703) detects temperature with the
thermistor (TH1,TH3) and controls reference voltage to the
APC circuit.

CIRCUIT DESCRIPTION

+B
Final AMP
Q1
+B
Final AMP
Q2
8T
IC2
APC
PC
Fig. 1 Final amplifier circuit: TK-5810H (B)
TK-5810H
Forward wave is detected by D2, and is converted into
DC voltage. The converted DC voltage is fed to the APC
comparator (IC2), and is compared with the PC voltage, then
is output from the OUT-B terminal (pin 7) of IC2 as an APC
voltage. The APC voltage controls the gate voltage of the
power module (IC1) and final amplifier (Q1,Q2), and keeps
transmission output stable.
If an abnormal antenna load is connected, reflected wave
is detected by D3, and output voltage (DC voltage) is fed to
the APC comparator (IC2). The transmission output is
reduced more as this DC voltage rises.
CM
COUPLER
D5,D6,D7
D2 D3
D8,D15,D16
FWD REFL
DET DET
VR1
(
B
ANT
LPF
ANT
SW
8T
)
7