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Icom IC-746 Service Manual

Icom IC-746
129 pages
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Table of Contents

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Questions and Answers:

Icom IC-746 Specifications

General IconGeneral
ModeSSB, CW, RTTY, AM, FM
Receiver TypeDouble conversion superheterodyne
Antenna ConnectorSO-239
Voltage13.8 V DC ±15%
Impedance50 ohms
Output Power100 W (SSB, CW, FM, RTTY), 40 W (AM)
Current DrainTX: 20 A
SensitivityAM: 2 µV
SelectivityCW: 500 Hz (-6 dB)

Summary

Introduction and Safety Information

Model Identification

Lists models and their symbols for identification.

Critical Safety Warnings

Essential precautions to prevent damage or injury during operation.

Service and Ordering Information

Ordering Replacement Parts

Guidelines for ordering spare parts for the transceiver.

Repair Notes and Precautions

Important notes and precautions for performing repairs.

Section 1: Specifications

General Specifications

Overall operating specifications and features of the transceiver.

Transmitter Specifications

Key performance parameters for the transmitter section.

Receiver Specifications

Key performance parameters for the receiver section.

Section 2: Inside Views

Main and RF Units Layout

Visual identification of components within the main and RF units.

PA and Control Units Layout

Visual identification of components within the PA and Control units.

Section 3: Disassembly and Option Installation

Transceiver Case Opening Procedure

Step-by-step guide for safely opening the transceiver case.

Optional Unit Installation

Instructions for installing optional voice synthesizer and IF filters.

High Stability Crystal Unit Installation

Procedure for installing the CR-282 high stability crystal unit.

Section 4: Circuit Description

RF Switching Circuits

Detailed explanation of RF switching circuit operations.

RF Filter Circuit (RF Unit)

Description of the RF filter circuits within the RF unit.

Receiver Section Circuitry

Overview of the receiver block diagram and its circuits.

Section 4: Circuit Description (Continued)

Mixer and RF Circuits

Description of first, second, and third mixer and RF circuits.

AM Demodulator and AF Selector Circuits

Explanation of AM demodulator and AF selector switch circuits.

Section 4: Circuit Description (Continued)

AF Amplifier and AGC Circuits

Details on the AF amplifier and Automatic Gain Control circuits.

Noise Blanker and S-Meter Circuits

Explanation of noise blanker and S-meter circuit operations.

Squelch Circuit Operation

Description of the squelch circuit's functionality.

Section 4: Circuit Description (Continued)

TUNIT PCB and Modulator Circuits

Description of TUNIT PCB and modulator circuits.

Tone Quelch and Speech Compressor Circuits

Explanation of tone quelch and speech compressor circuits.

AF/IF Amplifier and RF Circuitry

Details on AF/IF amplifier and RF circuits.

Transmitter Construction Overview

Overview of the transmitter's physical construction.

Section 4: Circuit Description (Continued)

ALC and PLL Circuitry

Explanation of ALC and Phase Locked Loop circuits.

Antenna Tuner and Power Supply Circuits

Description of antenna tuner and power supply circuits.

Section 4: Circuit Description (Continued)

Port Allocations: Main and Sub-CPU

Port assignments for the main unit and display board sub-CPU.

Port Allocations: Input/Output Expanders

Port assignments for input and output expanders.

Port Allocations: 1st LO DDS IC

Port assignments for the 1st LO DDS IC in the RF unit.

Section 4: Circuit Description (Continued)

RF Unit IC321 and Main Unit IC1709

Circuit description for RF Unit IC321 and Main Unit IC1709.

RF Unit IC1001 Circuitry

Explanation of the RF Unit IC1001 circuit.

Section 4: Circuit Description (Continued)

RF Unit IC321 Details

Further details on the RF Unit IC321 circuit.

Main Unit IC1709 Details

Further details on the Main Unit IC1709 circuit.

RF Unit IC1001 Details

Further details on the RF Unit IC1001 circuit.

Section 5: Adjustment Procedures

Required Test Equipment

List of essential test equipment for calibration procedures.

Test Equipment Connection Diagram

Diagram illustrating how to connect test equipment.

Section 5: Adjustment Procedures (Continued)

PLL Adjustment Procedures

Detailed steps for adjusting the PLL circuits.

PLL Adjustment Conditions and Measurement

Specific conditions and measurement points for PLL adjustments.

Section 5: Adjustment Procedures (Continued)

Main and RF Unit Adjustments (Top/Bottom)

Adjustment points on the top and bottom sides of main/RF units.

PA and Control Unit Adjustments (Top)

Adjustment points on the top side of PA and Control units.

Section 5: Adjustment Procedures (Continued)

Transmitter Adjustments: Initial Steps

Initial adjustments for transmitter parameters like idling current and peak power.

Transmitter Adjustments: Output Power

Procedures for adjusting HF and 144 MHz band output power.

Transmitter Adjustments: Gain and APC

Adjustments for transmitter total gain and IC APC control.

Section 5: Adjustment Procedures (Continued)

Transmitter Adjustments: Modulation and Carrier

Procedures for FM deviation, AM carrier level, and CW carrier adjustments.

Transmitter Adjustments: AM Power and SWR

Adjustments for AM carrier power, modulation, and SWR detection.

Section 5: Adjustment Procedures (Continued)

Unit-Specific Adjustment Locations

Diagrams showing adjustment points on Main/RF and PA/CTRL units.

Section 5: Adjustment Procedures (Continued)

Receiver Adjustments: Peak and Gain

Procedures for receiver peak and total gain adjustments.

Section 5: Adjustment Procedures (Continued)

Receiver Adjustments: Noise Blanker

Procedure for adjusting the noise blanker circuit.

Unit-Specific Adjustment Locations (Continued)

More diagrams showing adjustment points on Main/RF units.

Section 5: Adjustment Procedures (Continued)

Operational Mode Adjustments

Adjustments for various modes including transmitter, receiver, and level settings.

Preparation and Specific Adjustments

Preparation steps and specific controls for adjustments like PBT.

Section 6: Parts List - Unit Boards

Mic, PBT, RIT, Display Boards

List of parts for Mic, PBT, RIT, and Display boards.

Phone and S-Logic Boards

List of parts for Phone and S-Logic boards.

Section 6: Parts List - Unit Boards (Continued)

Display Board Parts

Additional parts listing for the Display board.

Mic and RF Board Parts

Parts list for Mic and RF boards.

PA Unit Parts

List of parts for the PA Unit.

Section 6: Parts List - Unit Boards (Continued)

PA Unit and Tuner Unit Parts

Parts list for PA Unit and Tuner Unit.

Control Unit and Unpacking Parts

Parts list for Control Unit and unpacking items.

Section 7: Mechanical Parts - Unit Assemblies

Front Unit Mechanicals

Mechanical components of the front unit assembly.

Board-Specific Mechanicals

Mechanical parts for Mic, PBT, RIT, Display boards.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Main and RF Unit Exploded Views

Exploded diagrams of the Main and RF units.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

S-Logic, Phone, and Display Boards

Exploded diagrams of S-Logic, Phone, and Display boards.

PBT and RIT Boards

Exploded diagrams of PBT and RIT boards.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Tenkey and Filter Boards Top View

Top view exploded diagrams of Tenkey and Filter boards.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Tenkey and Filter Boards Bottom View

Bottom view exploded diagrams of Tenkey and Filter boards.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Main Unit Top View Assembly

Exploded diagram of the Main Unit's top assembly.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Main Unit Top View Assembly Details

Further details on the Main Unit's top assembly components.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Main Unit Bottom View Assembly

Exploded diagram of the Main Unit's bottom assembly.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Main Unit Bottom View Assembly Details

Further details on the Main Unit's bottom assembly components.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

RF Unit Top View Assembly

Exploded diagram of the RF Unit's top assembly.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

RF Unit Top View Assembly Details

Further details on the RF Unit's top assembly components.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

RF Unit Bottom View Assembly

Exploded diagram of the RF Unit's bottom assembly.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

PA Unit Top View Assembly

Exploded diagram of the PA Unit's top assembly.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

PA Unit Top View Assembly Details

Further details on the PA Unit's top assembly components.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Control and Tuner Units Layout

Exploded diagrams of the Control and Tuner units.

Section 7: Mechanical Parts - Unit Assemblies (Continued)

Tuner Unit Assembly Details

Exploded diagram details of the Tuner Unit assembly.

Section 8: Semiconductor Information

Transistor and FET Symbols

Diagrams showing pinouts and symbols for transistors and FETs.

Section 8: Semiconductor Information (Continued)

Diode Symbols and Pinouts

Diagrams showing pinouts and symbols for various diodes.

Section 9: Board Layouts

S-Logic Board Top View

Component layout on the top side of the S-Logic board.

Section 9: Board Layouts (Continued)

S-Logic Board Layouts (Top & Bottom)

Component layouts for both top and bottom sides of the S-Logic board.

Section 9: Board Layouts (Continued)

PBT, RIT, and Mic Board Layouts

Component layouts for PBT, RIT, and Mic boards.

Section 9: Board Layouts (Continued)

Display Board Top View Layout

Component layout on the top side of the Display board.

Mode Board Layout

Component layout of the Mode board.

Phone Board Top View Layout

Component layout on the top side of the Phone board.

Section 9: Board Layouts (Continued)

Phone Board Bottom View Layout

Component layout on the bottom side of the Phone board.

Display Board Bottom View Layout

Component layout on the bottom side of the Display board.

PBT and RIT Board Layouts (Continued)

Additional component layouts for PBT and RIT boards.

Section 9: Board Layouts (Continued)

Tenkey and Filter Boards Top View Layout

Component layouts on the top side of Tenkey and Filter boards.

Section 9: Board Layouts (Continued)

Tenkey and Filter Boards Bottom View Layout

Component layouts on the bottom side of Tenkey and Filter boards.

Section 9: Board Layouts (Continued)

Main Unit Top View Component Layout

Component layout on the top side of the Main Unit.

Section 9: Board Layouts (Continued)

Main Unit Top View Component Layout (Details)

Further component layout details for the Main Unit top side.

Section 9: Board Layouts (Continued)

Main Unit Bottom View Component Layout

Component layout on the bottom side of the Main Unit.

Section 9: Board Layouts (Continued)

Main Unit Bottom View Component Layout (Details)

Further component layout details for the Main Unit bottom side.

Section 9: Board Layouts (Continued)

RF Unit Top View Component Layout

Component layout on the top side of the RF Unit.

Section 9: Board Layouts (Continued)

RF Unit Top View Component Layout (Details)

Further component layout details for the RF Unit top side.

Section 9: Board Layouts (Continued)

RF Unit Bottom View Component Layout

Component layout on the bottom side of the RF Unit.

Section 9: Board Layouts (Continued)

PA Unit Top View Component Layout

Component layout on the top side of the PA Unit.

Section 9: Board Layouts (Continued)

PA Unit Top View Component Layout (Details)

Further component layout details for the PA Unit top side.

Section 9: Board Layouts (Continued)

Control Unit Layout

Component layout of the Control Unit.

Tuner Unit Layout

Component layout of the Tuner Unit.

Section 9: Board Layouts (Continued)

Tuner Unit Assembly Layout Details

Exploded diagram details of the Tuner Unit assembly.

Section 10: Block Diagram

Main Unit Block Diagram

Overall functional block diagram of the Main Unit.

S-Logic Board Block Diagram

Functional block diagram of the S-Logic Board.

Section 10: Block Diagram (Continued)

Main Unit Block Diagram (Details)

Further details of the Main Unit's block diagram.

Display and Ten-Key Board Block Diagrams

Functional block diagrams for Display and Ten-key Boards.

Mode and Phone Board Block Diagrams

Functional block diagrams for Mode and Phone Boards.

Section 10: Block Diagram (Continued)

Main Unit Block Diagram (Sections)

Detailed block diagrams for different sections of the Main Unit.

Section 10: Block Diagram (Continued)

PA Unit Block Diagram

Functional block diagram of the PA Unit.

RF Unit Block Diagram

Functional block diagram of the RF Unit.

Section 10: Block Diagram (Continued)

Filter Unit Block Diagram

Functional block diagram of the Filter Unit.

Control Unit Block Diagram

Functional block diagram of the Control Unit.

Section 10: Block Diagram (Continued)

Tuner Unit Block Diagram

Functional block diagram of the Tuner Unit.

Section 11: Voltage Diagram

RF Unit Voltage Distribution

Diagram showing voltage distribution within the RF Unit.

Ten-Key and Front Unit Voltages

Voltage distribution for Ten-key and Front Units.

Section 11: Voltage Diagram (Continued)

Main Unit Voltage Distribution

Diagram showing voltage distribution within the Main Unit.

S-Logic Board Voltage Distribution

Voltage distribution for the S-Logic Board.

Section 11: Voltage Diagram (Continued)

Main Unit Voltage Distribution (Sections)

Detailed voltage distribution for various Main Unit sections.

Section 11: Voltage Diagram (Continued)

PA Unit Voltage Distribution

Diagram showing voltage distribution within the PA Unit.

RF Unit Voltage Distribution (Continued)

Further voltage distribution details for the RF Unit.

Section 11: Voltage Diagram (Continued)

Filter Unit Voltage Distribution

Diagram showing voltage distribution within the Filter Unit.

Control Unit Voltage Distribution

Voltage distribution for the Control Unit.

Section 11: Voltage Diagram (Continued)

Tuner Unit Voltage Distribution

Diagram showing voltage distribution within the Tuner Unit.

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