Name: Icom IC-751
Brand: Icom
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Table of Contents2
Specifications3
Operating Controls4
Front Panel4
Power Switch4
T/R (Transmit/Receive) Switch4
Top Cover8
Rear Panel Connections9
Operating Instructions10
How to Tune10
Preset10
Ham Band/General Coverage Selection10
Frequency Display on each Mode11
Tuning Control11
Dial Lock Switch12
VFO Switch12
Duplex (Split) Switch13
Transferring VFO Frequency13
RIT (Receive Incremental Tuning)13
XIT (Transmit Incremental Tuning)14
Memory Channel Operation15
Dial Function Select Switch (in VFO Mode)15
Memory Channel Selection15
Dial Function Select Switch (in Memory Channel Mode)16
Tuning by Up/Down Buttons on the Microphone17
Memory-Write (Programming the Memory Channels)17
Memory Clearing17
Frequency Control17
Scanning Operation18
Memory Channel Selecting18
Memory Scan18
Mode Selective Scan18
SSB Operation19
Resuming Scan19
Receiving19
NB (Noise Blanker)20
AGC (Automatic Gain Control)20
Preamp/Att Switch20
P.B. (Pass-Band) Tuning20
CW Operation21
Notch Filter21
Transmitting21
How to Use the Speech Processor21
RTTY Operation22
CW Side-Tone (Monitor)22
Break-In Operation22
AM Operation23
FM Operation23
General Coverage Receiver23
Other Operations24
VSWR Reading24
WWV Reception24
Simple Frequency Alignment24
Receive Antenna Terminals25
Transverter Connection25
Linear Amplifier Connection25
Cooling Fan25
Accessory (ACC) Socket ET26
Cautions26
Circuit Description27
Receiver Circuits27
RF Circuits/Connector/Rf Units27
IF Circuits27
Noise Blanker Circuit28
Filter Select Circuit28
FM Unit28
AF Circuit (Main Unit)29
AGC and Squelch Circuits29
Transmitter Circuits30
AF Circuits30
VOX Circuit30
ALC and Metering Circuits31
Power Supply Circuit31
RF Circuits32
PA Unit32
Filter/Connector Unit32
RF Unit Block Diagram32
Pll Unit33
Reference Frequency Oscillator and Marker Circuits33
PLL Sub-Loop Block Diagram33
Main Loop Circuits34
Pll IC34
Vco34
Loop System34
Sub-Loop35
Loop Filter and Mute Circuits35
In-Loop Local Oscillator Circuit35
Sub-Loop Block Diagram35
Logic Unit36
PLL Data36
Cpu36
How to Derive the N-Data36
CPU Pin Connection37
CPU Memory Map37
Custom IC Pin Connection37
I/O Expander Circuit38
N-Data of PLL38
High & Low N-Data Table38
N-Data Output Timing Chart38
Matrix Unit39
Y0 - DB0-DB3 (Ten Key)39
Y0 - DB4 (Scan Start/Stop)39
Y1 - Db4 (Vfo A/B)39
Y1 - DB5 (Memory Read)40
Y1 - DB6 (Ham/General)40
Y1 - DB7 (Rit On/Off)40
Y2 - DB8 (Function)40
Display Unit42
Display Unit Circuit42
Display Section43
DC-DC Converter Section43
Block Diagram44
Inside Views48
Top View48
Bottom View49
RF Unit49
Option Installations50
Installation of Optional Filter50
Optional Filters Prepared50
Assembly Procedure50
Built-In Power Supply Unit IC-PS3551
Voice Synthesizer Unit IC-EX31052
How the Voice Synthesizer Unit Works53
High-Stability Crystal Unit CR-6453
Mechanical Parts and Disassembly55
Front Panel Parts 157
Front Panel Parts 259
Front Panel Connector Connections61
Main Unit Side Connector Connections63
Logic-Pll Unit Side Connector Connections64
RF Unit Side Connector Connections65
Filter Unit Side Connector Connections66
Rear Panel Connector Connections67
Rear Panel Parts68
PLL Adjustment69
Main Unit (Common Circuits) Adjustment71
Main Unit72
Receiver Adjustment73
Transmitter Adjustment77
Meter Switch/Filter Units81
Voltage (Circuit) Diagrams82
Main Unit Circuit and Voltage Diagram82
Voltage Chart for Mode VS Filter Switch84
Local Oscillator Oscillating Level84
RF Unit Circuit and Voltage Diagram85
PLL Unit Circuit and Voltage Diagram87
PLL Sub-Loop Circuit and Voltage Diagram89
Logic Unit Circuit and Voltage Diagram90
PA Unit Circuit and Voltage Diagram93
Display Unit Circuit and Voltage Diagram95
Front Unit Circuit Diagram96
Matrix Unit Circuit Diagram98
Mode Switch98
Filter Unit Circuit Diagram100
Unit Wiring Diagram101
IC Ratings105
Pc1037H(Double Balanced Modulator)105
PC1181H (Audio Power Amplifier)105
LA2600 (Dual Attenuator)106
PD549C (Programmable Display Controller)106
Parts List112
Schematic Diagram138
Unit Layout163

Brand	Icom
Model	IC-751
Category	Transceiver
Language	English

Icom IC-751 Service Manual

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Icom IC-751 Specifications

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