Icom IC-746PRO User manual

HF/VHF TRANSCEIVER
i746PRO
SERVICE
MANUAL

INTRODUCTION
This service manual describes the latest service information
for the IC-746PRO HF/VHF TRANSCEIVER.
DANGER
NEVER connect the transceiver to an AC outlet or to a DC
power supply that uses more than 16 V. This will ruin the
transceiver.
DO NOT expose the transceiver to rain, snow or any liquids.
DO NOT reverse the polarities of the power supply when
connecting the transceiver.
DO NOT apply an RF signal of more than 20 dBm (100 mW)
to the antenna connector. This could damage the transceiv-
er’s front end.
ORDERING PARTS
Be sure to include the following four points when ordering
replacement parts:
1. 10-digit order numbers
2. Component part number and name
3. Equipment model name and unit name
4. Quantity required
<SAMPLE ORDER>
1110003870 S.IC NJM2058M-T1 IC-746PRO MAIN UNIT 5 pieces
8810005770 Screw BiH M3 × 8 ZK IC-746PRO Top cover 10 pieces
Addresses are provided on the inside back cover for your
convenience.
REPAIR NOTES
1. Make sure a problem is internal before disassembling the
transceiver.
2. DO NOT open the transceiver until the transceiver is
disconnected from its power source.
3. DO NOT force any of the variable components. Turn
them slowly and smoothly.
4. DO NOT short any circuits or electronic parts. An insu-
lated tuning tool MUST be used for all adjustments.
5. DO NOT keep power ON for a long time when the trans-
ceiver is defective.
6. DO NOT transmit power into a signal generator or a
sweep generator.
7. ALWAYS connect a 50 dB to 60 dB attenuator between
the transceiver and a deviation meter or spectrum ana-
lyzer when using such test equipment.
8. READ the instructions of test equipment thoroughly
before connecting equipment to the transceiver.
To upgrade quality, any electrical or mechanical parts and
internal circuits are subject to change without notice or
obligation.

TABLE OF CONTENTS
SECTION 1 SPECIFICATIONS
SECTION 2 INSIDE VIEWS
SECTION 3 DISASSEMBLY AND OPTION INSTALLATIONS
SECTION 4 CIRCUIT DESCRIPTION
4 - 1 RECEIVER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 1
4 - 2 TRANSMITTER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 - 4
4 - 3 PLL CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 6
4 - 4 ANTENNA TUNER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 7
4 - 5 POWER SUPPLY CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 8
SECTION 5 ADJUSTMENT PROCEDURES
5 - 1 PREPARATION BEFORE SERVICING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1
5 - 2 PLL ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 2
5 - 3 TRANSMITTER ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 4
5 - 4 RECEIVER ADJUSTMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 8
5 - 5 ADJUSTMENT MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 10
SECTION 6 PARTS LIST
SECTION 7 MECHANICAL PARTS
SECTION 8 SEMI-CONDUCTOR INFORMATION
SECTION 9 BOARD LAYOUTS
9 - 1 S-LOGIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 1
9 - 2 DISPLAY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 3
9 - 3 TEN-KEY BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5
9 - 4 MODE BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5
9 - 5 PHONE BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5
9 - 6 RIT BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5
9 - 7 PBT BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5
9 - 8 MIC BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 6
9 - 9 MAIN UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 7
9 - 10 DSP UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 9
9 - 11 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 11
9 - 12 CTRL UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 13
9 - 13 TUNER UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 15
9 - 14 PA UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 17
9 - 15 FILTER UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
9 - 16 DRV BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
9 - 17 VARISTOR-A BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
9 - 18 VARISTOR-B BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
9 - 19 VARISTOR-C BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
9 - 20 VARISTOR-D BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 19
SECTION 10 BLOCK DIAGRAM
SECTION 11 WIRING DIAGRAM
SECTION 12 VOLTAGE DIAGRAMS
12 - 1 DSP UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 1
12 - 2 FRONT UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 2
12 - 3 MAIN UNIT (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 3
12 - 4 MAIN UNIT (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 4
12 - 5 PA UNIT, FILTER, DRV AND VARISTOR BOARDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 5
12 - 6 CTRL AND TUNER UNITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 6
12 - 7 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 7

SECTION 1 SPECIFICATIONS
1 - 1
■GENERAL
• Frequency coverage:
Receive 0.030– 60.000 MHz*1, *2
108.000–174.000 MHz*1, *2
Transmit 1.800– 1.999 MHz*23.500– 3.999 MHz*2
7.000– 7.300 MHz*210.100–10.150 MHz*2
14.000– 14.350 MHz*218.068–18.168 MHz*2
21.000– 21.450 MHz*224.890–24.990 MHz*2
28.000– 29.700 MHz*250.000–54.000 MHz*2
144.000–148.000 MHz*2
*1Except for some frequency ranges.
*2Depending on version.
• Mode : USB, LSB, CW, RTTY, AM, FM
• Number of memory channels:
101 (99 regular, 1 call, 2 scan edges)
• Antenna connector : SO-239 ✕3 (2 for HF/50 MHz bands
and 1 for 144 MHz band; 50 Ω)
•Usable temp. range: –10˚C to +60˚C (14˚F to 140˚F)
•Frequency stability : Less than ±7 ppm from 1 min. to 60
min. after power ON. After that the
rate of stability change is less than ±1
ppm at 25˚C (+77˚F). Temperature
fluctuations (0˚C to +50˚C; 32˚F to
122˚F) less than ±5 ppm.
•Freq. resolution : 1 Hz
•Power supply requirement:
13.8 V DC ±15 % (negative ground)
•Current consumption:Transmit max. power 23.0 A
Receive stand-by 2.2 A
max. audio 3.0 A
•Dimensions : 287(W) ✕120(H) ✕316.5(D) mm
115⁄16(W) ✕423⁄32(H) ✕1215⁄32(D) in
•Weight : 9.0 kg (19 lb 13 oz)
•ACC 1 connector : 8-pin DIN connector
•ACC 2 connector : 7-pin DIN connector
•
REMOTE connector : 2-conductor 3.5(d) mm (1⁄8")
■TRANSMITTER
•Output power : SSB/CW/RTTY/FM 5–100 W
AM 5–40 W
•Modulation system :
SSB PSN modulation
AM Low power modulation
FM Phase modulation
•Spurious emission : Less than –50 dB (HF bands)
Less than –60 dB (
50/144 MHz bands )
•Carrier suppression: More than 40 dB
•Unwanted sideband suppression:
More than 55 dB
•∆TX variable range : ±9.99 kHz
•Mic. connector : 8-pin connector (600 Ω)
•
ELE-KEY connector : 3-conductor 6.35(d) mm (1⁄4")
•KEY connector : 3-conductor 6.35(d) mm (1⁄4")
•SEND connector : Phono (RCA)
•ALC connector : Phono (RCA)
■RECEIVER
•Receive system : Triple-conversion superheterodyne
•Intermediate frequencies:
1st IF freq. 64.455 MHz
2nd IF freq. 455 kHz
3rd IF freq. 36 kHz
•Sensitivity (typical) :
SSB, CW, RTTY (10 dB S/N)
1.8–29.99000 MHz*10.16 µV
50.0–54.0000 MHz*20.13 µV
144.0–148.0000 MHz*30.11 µV
AM (10 dB S/N) 0.5–1.799999 MHz 13 µV
1.8–29.99000 MHz*12.0 µV
50.0–54.0000 MHz*21.0 µV
144.0–148.0000 MHz*31.0 µV
FM (12 dB SINAD)
28.0–29.9900 MHz*10.5 µV
50.0–54.0000 MHz*20.25 µV
144.0–148.0000 MHz*30.18 µV
*1Pre-amp 1 ON *2Pre-amp 2 ON *3Pre-amp ON
•Squelch sensitivity (Pre-amp OFF):
SSB/CW/RTTY Less than 5.6 µV
FM Less than 1.0 µV
•Selectivity (typical) :
SSB (at 2.4 kHz bandwidth)
More than 2.4 kHz/–6 dB
Less than 3.2 kHz/–40 dB
Less than 3.6 kHz/–60 dB
Less than 4.3 kHz/–80 dB
CW (at 500 Hz bandwidth)
More than 500 Hz/–6 dB
Less than 700 Hz/–60 dB
RTTY (at 350 Hz bandwidth)
More than 360 Hz/–6 dB
Less than 650 Hz/–60 dB
AM (at 6 kHz bandwidth)
More than 6.0 kHz/–6 dB
Less than 15.0 kHz/–60 dB
FM (at 15 kHz bandwidth)
More than 12 kHz/–6 dB
Less than 20 kHz/–60 dB
•Spurious and image rejection ratio:
More than 70 dB (HF/50 MHz band)
(except IF through in 50 MHz band)
More than 60 dB (144 MHz band)
•RIT variable range : ±9.99 kHz
•Audio output power (at 13.8 V):
More than 2.0 W at 10 % distortion
with an 8 Ωload
•PHONES connector: 3-conductor 6.35 (d) mm (1⁄4")
•EXT SP connector : 2-conductor 3.5 (d) mm (1⁄8") 8 Ω
All stated specifications are subject to change without notice or obligation.

to S-LOGIC
board J303
DS1002
9-2 DISPLAY BOARD
•TOP VIEW
9 - 3

1-1-32, Kamiminami, Hirano-ku Osaka 547-0003, Japan S-13811HZ-C1
©2002 Icom Inc.

Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf
Icom IC-746 PRO _sm02.pdf