Icom IC-M401E, Руководство по обслуживанию

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4 - 4
4-3-2 TX AND RX LOOP (MAIN-E UNIT)
The generated signal at the VCO (Q4, Q5, D3, D4) enters
the PLL IC (IC1, pin 2) and is divided at the programmable
divider section and is then applied to the phase detector
section.
The phase detector compares the input signal with a refer-
ence frequency, and then outputs the out-of-phase signal
(pulse-type signal) from pin 8.
The pulse-type signal is converted into DC voltage (lock
voltage) at the loop filter (R7–R9, R41, C4, C5, C43, C44),
and is then applied to varactor diodes (D3, D4) of the VCO
to stabilize the oscillated frequency.
4-3-4 VCO CIRCUIT (MAIN-E UNIT)
The VCO outputs from Q4, Q5 are buffer-amplified at the
buffer amplifiers (Q6 and Q7), and are then sent to the Tx/Rx
switch (D7 and D8). The receive LO signal is applied to the
1st mixer circuit (Q22) through a low-pass filter, and the
transmit signal is applied to the pre-drive amplifier (Q10). A
portion of the VCO output is reapplied to the PLL IC (IC1, pin
2) via the buffer amplifier (Q3).
4-4 ATIS AND DSC CIRCUITS
4-4-1 ATIS ENCODE CIRCUIT
(LOGIC-E BOARD AND MAIN-E UNIT)
The FSK signal of ATIS created at CPU (LOGIC-E board;
IC1) is passed through the ladder type D/A convertor
(R41–R56) to convert into the analog signal. The analog sig-
nal is applied to the buffer amplifier (LOGIC-E board; IC9),
and then applied to the mixer circuit (MAIN-E unit; IC7, pins
1, 2) to mix with signals from the microphone. The signal
passes through the low-pass filter (MAIN-E unit; IC8, pins 1,
3) and is then applied to the VCO circuit as modulation sig-
nal.
4-4-2 DSC ENCODE CIRCUIT (MAIN-E UNIT)
The DSC signal created at the optional DSC controller (DS-
100) is applied to the T1 via the J7, and then as floating sys-
tem output. The signal is applied to the buffer amplifier
(Q61), and then passes through the 6 dB/oct pre-emphasis
circuit (R417, C416). The signal is applied to the mixer cir-
cuit (IC7, pins 1, 2) to mix with signals from the microphone.
The signal passes through the low-pass filter (IC8, pins 1, 3)
and is then applied to the VCO circuit as modulation signal.
4-5 LOGIC CIRCUITS (LOGIC-E BOARD)
• CPU
IC1 is an 8 bit signal chip micro-computer and contains LCD
driver, serial I/O, timer, A/D converter, programmable I/O,
ROM and RAM.
• SYSTEM CLOCK CIRCUIT
X1 is a ceramic oscillator and oscillate 9.8304 MHz system
clock for the CPU (IC1).
• RESET CIRCUIT
IC2 is a reset IC. When turn power ON, IC2 outputs a reset
signal (“LOW” pulse) to the CPU (IC1, pin 15) via the “RES”
line.
• LOW BATTERY DETECTOR
VCC voltage is divided by R84, R85 and is applied to the low
battery detector section in the CPU (IC1, pin 91) via the
“LBAT” line.
• DIMMER CIRCUIT
The CPU (IC1), Q1, Q2 and Q3 are dimmer circuit and con-
trol the 4 steps the LCD backlight (DS2–DS7).
4-6 POWER SUPPLY CIRCUITS
VOLTAGE LINES
LINE
HV
HVS
VCC
5V
T5
R5
R8
DESCRIPTION
The voltage from the connected DC power sup-
ply.
Same voltage as the HV line which is passed
through the [PWR] switch (VR unit; R1).
Same voltage as the HVS line. The voltage is
applied to the optional DSC controller (DS-100).
Common 5 V converted from the VCC line at the
5V regulator circuit (MAIN-E unit; IC10).
Transmit 5 V controlled by the T5 control circuit
(MAIN-E unit; Q52, Q57) using the “SEND” sig-
nal from the CPU (LOGIC-E board; IC1). The
controlled voltage is applied to the transmitter
circuit.
Receive 5 V controlled by the R5 control circuit
(MAIN-E unit; Q53, Q54) using the “RCV” signal
from the CPU (LOGIC-E board; IC1). The con-
trolled voltage is applied to the receiver circuit.
Receive 8 V controlled by the R5 control circuit
(MAIN-E unit; Q55, Q56) using the “R5” signal.
The controlled voltage is applied to the receiver
circuit.