Kenwood NXR-5700, Service Manual

Page: 13 / 122

(No.RA033<Rev.001>)1-13
2.6.2.6 Driver circuit
The driver circuit amplifies the transmitter frequency signal to the level required for input to the Final Unit (XC3-015 A/5).
This circuit consists of RF amplifiers Q201, Q202 and Q204, switches Q203, Q207 and Q208, and operating amplifier IC201.
DC switches Q207 and Q208 turn the power supply voltage of RF amplifiers Q201, Q202, and Q204 on and off.
Q204 output power is controlled by IC201 and "DRV_PWR" signal from IC801. Q204 output power is +16dBm.
This output level is output from the driver output connector CN207 and connected to the Final Unit (XC3-015 A/5).
Fig.6 Driver circuit
2.6.2.7 Modulation level adjustment circuit
The level adjustment circuit adjusts the modulation signal level to provide the required level of modulation. This circuit consists of
IC101, IC302, IC801.
The modulation audio signal comes from the Control Unit (XC1-064) through CN722 pin1.
IC801 is an electronic volume control IC. Deviation of Transmitter main VCO and 16.8MHz modulation PLL is adjusted by IC801.
Subaudible modulation signal is fed to 16.8MHz modulation PLL. IC302 is an inverting amplifier of the modulating signal, and inverting
amplifier of synthesizing the VCXO (X301) control voltage and modulating signal.
Audible modulation signal is fed to transmitter main VCO. IC101 is an non-inverting amplification of modulating signal. And it add to
TX_ASSIST voltage of IC102 output.
Fig.7 Modulation level adjustment circuit
2.6.2.8 AVR circuit
IC806, IC807, IC808, IC809, IC812 and IC813 are AVR ICs.
IC806 is DC/DC converter IC to produce 20V for VCO. The 20V power supply is filtered by Q101.
IC813 is used for optional OCXO unit.
IC608 and IC803 are voltage reference IC. IC803 is used for AD converter's voltage reference. IC608 is used for internal VCTCXO's
frequency control DA converter's voltage reference.
Fig.8 AVR circuit
ATT ATT ATT
DET
SW
A/2
B/2
DRV_PWR
TX main
PLL circuit
136~
174MHz
Q201
Q201
Q204
Q207,Q208
D202
CN207
136~174MHz
+16dBm
Final
unit
IC201
IC201
80C_2
80C_2
80C_2
Control
unit
Mod
Signal
CN722
1pin
IC801
33MPU
1
33C
IC302
( 1/2 )
33C
IC302
( 1/2 )
TX Mod 16.8MHz
PLL circuit
VCXO_CV
TX main
PLL circuit
VCO TX_ASSIST
24
22
23
33C
IC101
( 1/2 )
TX Mod 19.2MHz
PLL CP
+B
SW
Q810,Q811
IC813
CN804
8V
OCXO
IC812
IC808
80C_2
80C
IC809
50C
IC807
33C
IC806
DC/DC Con.
200C
Ripple
Filter
80C_1
+13.6V
CN803
8V
8V_2
8V
8V_1
5V
3.3V
20V