Transmitter Circuits - Icom IC-7600 Service Manual

RX AF CIRCUITS (MAIN UNIT)
The AF signals from the buffer amplifier are applied to
the AF AMP (IC2301) via the squelch gate (Q2361). The
amplified AF signals are applied to the Voltage Controlled
Amplifier (VCA; IC2231) to be adjusted its level (=audio
output level).
The level-adjusted AF signals are applied to the AF power
AMP (IC2312) via the LPF (Q2312).
• RX AF CIRCUITS
J7
PHO/AFO
[PHONES]
[EXT-SP]
I NT. SP
SP1
CHASSIS

3-2 TRANSMITTER CIRCUITS

TX AF CIRCUITS (MAIN UNIT)
The audio signals from the microphone (MIC signals)
are applied to the MAIN UNIT via the MICROPHONE
CONNECTOR (MIC BOARD; J1), and applied to the Voltage
Controlled Amplifi er (VCA; IC2601).
The applied MIC signals are amplifi ed by internal MIC AMP,
and adjusted its level (=MIC gain) by internal VCA circuit.
The level-adjusted MIC signals are passed through the
MIC line selector (IC4101), and amplified by the AF AMP
(IC4205), then applied to the modulation circuits.
The signals from the external equipment connected to the
accessory socket [ACC1] on the rear panel, are directly
applied to the AF AMP (IC4205) via the MIC line selector
(IC4101).
• TX AF AND MODULATION CIRCUITS
IC2601
MC 1
MIC_IN
MIC
AMP
MIC BOARD MIC GAIN ADJ.
CP1
ACC(1)
MOD
IC2312
RL2302
PWR
LPF
AMP
AF mute SW
IC4101
IC4205
AF
AM P
VCA
MIC LINE SELECT
The power-amplifi ed AF signals are passed through the AF
mute switch (RL2302), then applied to the internal speaker
or external speaker jack (J2302) on the rear panel or
headphone jack (JACK BORD J2) on the front panel.
IC2331 IC2331 IC2301
AF
AM P
VCA
AM P
The amplified MIC signals are applied to the modulation
circuits.
MODULATION CIRCUITS AND DSP (MAIN UNIT)
The MIC signals from the TX AF circuits are applied to the
Balance-Unbalance converter (Balun; IC4201, 4204), and
the converted MIC signals are applied to the A/D converter
(IC4301) to be converted into the digital signal.
The converted digital signal is applied to the DSP (IC5001)
and modulated and processed.
The modulated signal is converted into the analog signal by
the D/A converter (IC4301), and passed through the balun
(IC4401) to be converted into the 3rd TX IF signal.
The converted 3rd TX IF signal is applied to the 3rd TX IF
circuits.
IC4201,
IC4204
IC4301 IC5001
A/D
BALUN DSP
(CODEC)
MAIN UNIT
3 - 3
Q2361
From the demodulation circuits
Squelch gate
3rd TX IF->
IC4301
IC4401
3rd TX IF circuits
D/A
BALUN
(CODEC)