Driver And Final Power Amplifi Er Circuit; Other Circuit; Final Unit - Kenwood NXR-710 Service Manual

+B
from Final unit
(X45-392 A/3)
+B,SB
to Control unit
(X53-449)

2-10. Other circuit

■ EEPROM
The EEPROM (IC802) has a data capacity of 2Kbit. It
stores the tuning data in frequency adjustment.
■ Temperature sensor
The temperature sensor (IC800) monitors temperature
around the VCTCXO (X500).
■ I/O expander
The I/O expander IC (IC805) controls power sources, fan,
analogue switches, and the transmit power control circuit.
IC805 is controlled by the MCU which is in the Control unit
(X53-449).
■ Electronic volume control IC
The Electronic volume control IC (IC804) adjusts the
modulating signal, center frequency of the front-end BPF,
and the power of the RF fi nal amplifi er. IC804 is controlled
by the MCU which is in the Control unit.
LPF
TX ANT
CIRCUIT DESCRIPTION
CN701
Q702,Q703
SW
SBC
CN700
SB
Fig. 11 AVR circuit
CM coupler
REV DET FW DET
D4 D3
FW DET
REV DET
Fig. 12 Driver and Final power amplifi er circuit
IC702
8V AVR
IC701
15V DC/DC
Q700,Q701
SW
RXC
5V AVR
Q705,Q706
IC700
SW
RXC
3.3V AVR

3. Final unit

The RF final amplifier unit (X45-3920-10) amplifies the
transmitter power to a specifi ed level.
This unit consists of the following circuits:
(1) Driver and Final power amplifi er circuit
(2) CM coupler circuit
(3) Filter circuit
(4) APC circuit
(5) High temperature detector circuit
(6) FAN action control circuit
(7) AVR circuit
3-1. Driver and Final power amplifi er circuit
The transmit signal from the TX IN terminal CN1 of the
Final unit (X45-392) is amplifi ed by Q1, Q2 and Q3, and is
passed to the final stage Q4. The signal amplified by the
fi nal stage Q4 passes through the CM coupler circuit and
fi lter circuit, and is then fed to the antenna.
+B
Final AMP Drive AMP
Q4 Q3
Drive AMP
Vcont
Q2
Auto power control
Limiter AMP
IC201(B/2)
DC AMP
IC202(A/2)
Buffer AMP
IC202(B/2)
NXR-710
80C
Ripple Filter 80C_1
Ripple Filter 80C_2
Ripple Filter 150C_1
Ripple Filter
150C_2
80R
50C
50R
IC704
3V AVR
30R
33C
IC703
80T
CN1
CN801
Drive AMP
8TC
Q1
FAN
80T
ASWC
PLIM
RAMP
PRE AMP
IC201(A/2)
FDT
Temp1
TH201
13