Icom IC-756PRO Service Manual

HF/50MHz ALL BAND TRANSCEIVER
i756PRO
SERVICE
MANUAL

Icom IC-756PRO Specifications

General

Type	HF/50MHz Transceiver
Supply Voltage	13.8 V DC
Receiver Type	Triple conversion superheterodyne
Frequency Range	0.03-60 MHz
Modes	SSB, CW, AM, FM, RTTY
Selectivity	2.4 kHz (SSB), 6 kHz (AM)
Image Rejection	70 dB
Current Drain	20 A (max)
Intermediate Frequencies	455 kHz

Summary

INTRODUCTION

DANGER

Critical safety warnings for transceiver operation and handling.

SECTION 1 SPECIFICATIONS

GENERAL

Covers frequency coverage, modes, memory channels, connectors, and power.

RECEIVER

Details receiver system, frequencies, sensitivity, and selectivity.

TRANSMITTER

Lists transmitter output power, modulation system, and emissions.

ANTENNA TUNER

Specifies antenna tuner impedance range, input power, and loss.

SECTION 2 INSIDE VIEWS

BOTTOM VIEW

Identifies components from the bottom view of the transceiver.

TOP VIEW

Identifies components from the top view of the transceiver.

SECTION 3 CIRCUIT DESCRIPTION

3-1 RECEIVER CIRCUITS

Explains signal path from antenna through receiver stages to DSP.

3-2 TRANSMITTER CIRCUITS

Details signal path from microphone input to antenna output.

3-3 PLL CIRCUITS

Describes PLL unit functions for generating local oscillator frequencies.

3-6 POWER SUPPLY CIRCUITS

Lists voltage lines and descriptions for various transceiver units.

SECTION 4 ADJUSTMENT PROCEDURES

4-1 PREPARATION BEFORE SARVICING

Lists required test equipment and connection diagrams for servicing.

4-2 PLL ADJUSTMENTS

Step-by-step procedures for adjusting PLL circuit parameters.

4-3 RECEIVER ADJUSTMENTS

Procedures for tuning receiver peak, mixer balance, and FM distortion.

4-4 TRANSMITTER ADJUSTMENTS

Procedures for adjusting transmitter idling current, peak, and output power.

4-5 TUNER ADJUSTMENT

Procedures for adjusting the SWR detector and tuner calibration.

SECTION 5 PARTS LIST

[FRONT UNIT]

Lists mechanical and electronic parts for the front unit.

[DISPLAY BOARD]

Lists components for the display board.

[RF UNIT]

Lists components for the RF unit.

[MAIN UNIT]

Lists components for the main unit.

[PLL UNIT]

Lists components for the PLL unit.

SECTION 6 MECHANICAL PARTS

[FRONT UNIT]

Lists mechanical parts for the front unit.

[CHASSIS PARTS]

Lists general chassis parts.

[RF UNIT]

Lists mechanical parts for the RF unit.

[PLL UNIT]

Lists mechanical parts for the PLL unit.

SECTION 8 BOARD LAYOUTS

8-1 PBT, RIT AND MIC BOARDS

Shows component placement for PBT, RIT, and MIC boards.

8-2 DISPLAY BOARD

Shows component placement for the display board.

8-4 RF UNIT (TOP VIEW)

Shows component placement for the RF unit (top view).

8-5 PLL UNIT (TOP VIEW)

Shows component placement for the PLL unit (top view).

8-6 MAIN UNIT (TOP VIEW)

Shows component placement for the main unit (top view).

SECTION 9 BLOCK DIAGRAM

BOARD BOARD

Illustrates the overall system architecture and interconnections.

SECTION 10 VOLTAGE DIAGRAM

10-1 FRONT UNIT

Voltage distribution diagram for the front unit.

10-2 DSP BOARD

Voltage distribution diagram for the DSP board.

10-4 MAIN UNIT (1)

Voltage distribution diagram for the main unit (part 1).

10-6 PLL UNIT

Voltage distribution diagram for the PLL unit.

10-8 RF UNIT

Voltage distribution diagram for the RF unit.