Transmitter Circuits; Tx Af Circuits (Connect Unit); Modulation Circuits (Main Unit); Tx Af Circuits (Main Unit) - Icom IC-7410 Service Manual

RX AF CIRCUITS (CONNECT UNIT)
• AUDIO OUTPUT FROM THE SP/HEADPHONES
The AF signal from the demodulator circuits is applied to
the AF AMP (IC221), through the squelch gate (Q231).
The amplifi ed AF signal is applied to the Voltage Controlled
Amplifi er (VCA; IC301) to be adjusted in level (=audio output
level).
The level-adjusted AF signal is applied to the AF power AMP
(IC351), through the mute SW (Q331) and AF SW (Q321).
The amplified AF signal is passed through the AF mute
switch (Q371), and then applied to the internal speaker or
external speaker jack (J101), or the amplified AF signal is
applied to the headphones jack (JACK BORD: J2).
• RX AF CIRCUITS
IC351
Q371 Q321 Q331
[EXT-SP]
AF
AF AF MUTE
AMP
SW SW
J101
Internal
Q326
speaker
SP1
AF
AF
AMP SW
[PHONES]
J2(JACK UNIT)
I C301
From the
Q231
I C221
modulator
circuits
SQL
AMP
VCA AMP
SW GATE
CONNECT UNIT

3-2 TRANSMITTER CIRCUITS

TX AF CIRCUITS (MAIN UNIT)

The audio signal from the microphone (MIC signal) is
applied to the MAIN UNIT, through the MICROPHONE
CONNECTOR (MIC BOARD; J1), and then applied to the
Voltage Controlled Amplifi er (VCA; IC3401).
The applied MIC signal is amplified by the MIC AMP, and
adjusted in level (=MIC gain) by the VCA circuit.
The level-adjusted MIC signal is passed through the MIC
line SW (IC3421), amplifi ed by the AF AMP (IC3452), and
then applied to the modulation circuits, through the two LPFs
(IC3452).
The MIC signal from the accessory socket [ACC1] on the
rear panel, is directly applied to the AF AMP (IC3452),
through the MIC line SW (IC3421).
The amplified MIC signal is applied to the modulation
circuits.
• TX AF CIRCUITS
IC3401
FRONT PANEL
MIC
MIC
VCA
AMP
CONNECT UNIT
AMP
VCA

MODULATION CIRCUITS (MAIN UNIT)

The MIC signal from the TX AF circuits is passed through
the Balance-Unbalance converter (Balun; IC4401, IC4402),
and then applied to the CODEC (IC4461), to be converted
into digital audio signal.
The converted digital audio signal is applied to the DSP
(IC4001), and processed and modulated.
The modulation signal is converted into analog audio signal
by the CODEC (IC4651), and then applied to the 3rd TX IF
circuits as the 3rd TX IF signal.
• MODULATION CIRCUITS
I C4402
DSP_MOD IN
LPF
I C4401
I C4402
From the TX AF
circuits
BUFF LPF
3 - 3
IC3421
I C3452 I C3452
IC3452
AMP LPF LPF
I C4001 I C4651
I C4461
To the 1st TX IF
circuits
DSP
To the modulation
circuits