Icom IC-7400, Service Manual, Page: 16 / 92

4 - 8
(1) CPU and EEPROM (CTRL unit)
The antenna tuner CPU (IC5) controls the tuning motors via
the motor driver circuit (Q211–Q218) and tuning relays di-
rectly, and memorizes the best preset position in 100 kHz
steps. The memory contents are stored in the EEPROM
(IC6) without a backup battery.
(2) Tuning motors (CTRL unit)
The motor driver circuit (Q211–Q218) rotates the tuning mo-
tors (MF1, MF2) to obtain a low SWR.
(3) Tuning relays (TUNER unit)
According to the operating frequency band and antenna con-
dition, tuning relays select the capacitors (C34–C43) and
coils ( L3–L9, L11, L12).
4-5 POWER SUPPLY CIRCUITS
4-5-1 PA UNIT
4-5-2 S-LOGIC BOARD
4-5-3 MAIN UNIT
4-5-4 PLL UNIT
4-4-4 ANTENNA TUNER CPU PORT ALLOCATION
(CTRL unit; IC5)
1
2
3
4
7
13
15
17
19
21
22, 23
25,
34–36
38–40
26–32
41–44
45–48
64
Input port for the resistance com-
ponents detection voltage.
Input port for the reflected RF
power voltage.
Inpout port for the forward RF
power voltage.
Input port for the transceiver power
OFF.
Input port for the reference voltage
setting.
Outputs tuner data signal.
Input port for the serial signal.
Outputs the [TUNER] ON/OFF sig-
nal.
Input port for reset signal.
Input port for the TX/RX switching
signal.
Input ports for the antenna tunner
CPU system clock.
Output the capacitor selection sig-
nals.
Output the coil selection signals.
Output ports for the tuning motor
(MF2) drive signals.
Output ports for the tuning motor
(MF1) drive signals.
Input port for the reactance compo-
nents detection voltage.
AN2
AN1
AN0
PWRS
SETI
CIKY
CIST
THRU
CDRS
TRC
XIN, XOUT
NVHF, CO3,
CO2, CO1,
CI3, CI2, CI1
VHF, 24M,
18M, 14M,
10M, 7M, 4M
P07–P04
P03–P00
AN3
Pin Port
Description
number name
Line Description
–8 V
Common –8 V converted from the 14V line and
regulated by the –8 V DC-DC converter (IC401).
Line Description
H14V
The voltage from an external power supply via
the common filter circuit (FILTER board, L1).
HV
The same voltage as the H14V line passed
through a fuse.
14VS
The same voltage as the HV line passed through
the switching relay (RL1).
14V
The same voltage as the 14VS line passed
through coils (L22, L23).
8V
Common 8 V converted from the 14V line and
regulated by the +8 regulator circuit (IC3).
5V
Common 5 V converted from the 14V line and
regulated by the +5 regulator circuit (IC2).
H5V
Common 5 V converted from the HV line and
regulated by the +5 regulator circuit (IC1).
Line Description
R8V
Receive 8 V converted from the 14V line and
regulated by the R8V regulator circuit (Q451,
Q453).
T8V
Transmit 8 V converted from the 14V line and
regulated by the T8V regulator circuit (Q450,
Q452).
Line Description
5VPLL
Common 5 V converted from the 8V line and
regulated by the 5 V regulator circuit (IC1051).