ICOM SERVICE MANUAL

INTRODUCTION

This service manual describes the latest service information for the IC-12GAT/GE 1200MHz FM TRANSCEIVER at the time of going to press. This service manual covers both the IC-12GAT and IC-12GE.

TABLE OF CONTENTS

• SECTION 1 INSIDE VIEWS (1-1~1-2)
• 1-1 MAIN UNIT (1-1)
• 1-2 RF UNIT (1-2)
• 1-3 SPEAKER AND DTMF UNITS (1-2)
• SECTION 2 MECHANICAL PARTS AND DISASSEMBLY (2-1~2-2)
• SECTION 3 ADJUSTMENT PROCEDURES (3-1~3-6)
• 3-1 PREPARATION BEFORE SERVICING (3-1)
• 3-2 PLL ADJUSTMENT (3-3)
• 3-3 RECEIVER ADJUSTMENT (3-4)
• 3-4 TRANSMITTER ADJUSTMENT (3-5)
• SECTION 4 BOARD LAYOUTS (4-1~4-8)
• 4-1 LOGIC UNIT (4-1)
• 4-2 MAIN UNIT (4-3)
• 4-3 RF UNIT (4-5)
• 4-4 ATTACHED UNITS (RF UNIT) (4-7)
• 4-5 DTMF AND TONE UNITS (IC-12GAT ONLY) (4-8)
• SECTION 5 PARTS LIST (5-1~6)
• SECTION 6 VOLTAGE DIAGRAM (6-1)

SECTION 1 INSIDE VIEWS

1-1 MAIN UNIT

IC-12GAT: Internal view showing the Audio filter de-emphasis circuit, +5 V, T/R regulator, T/R mute circuit, SUBAUDIBLE TONE ENCODER UNIT (IC-12GAT only), AF power amp circuit, and Microphone amp circuit.

IC-12GE: Internal view showing the Tone call circuit (IC-12GE only).

1-2 RF UNIT

Internal view of the RF Unit, highlighting the RF amp circuit, Antenna switching IC (IC1: MD004), LPF circuit, APC circuit, Power module (IC5: SC-1083), Filter B circuit, PLL circuit, 2nd LO crystal (X1: CR-241 71.745 MHz), IF circuit, and VCO UNIT.

1-3 SPEAKER AND DTMF UNITS

Speaker and DTMF Units: Shows the Speaker (SP201: Si36D04), Microphone (MC201: KUC2023-01-006), DTMF UNIT (IC-12GAT only), DTMF encoder crystal (X801: 3.58 MHz), and DTMF encoder IC (IC801: LR40872).

SECTION 2 MECHANICAL PARTS AND DISASSEMBLY

This section details the mechanical parts and their ordering numbers. The following table lists key components:

Screw type: Screw: M2 × 5, etc. Screw head style: PH: Pan head. Self-tapping screw: B02×31.5, etc. Precision type screw: No. 0-3, etc. FH: Flat head. BuH: Button head.

Diagrams: The document includes exploded view diagrams for CASE AND FRONT PANELS, TOP PANEL, LOGIC-A AND LOGIC-B UNITS, MAIN UNIT, RF UNIT, and CONTACT HOLDER, illustrating the assembly and placement of the parts listed above.

SECTION 3 ADJUSTMENT PROCEDURES

3-1 PREPARATION BEFORE SERVICING

REPAIR NOTE:

• Make a promise is internal before disassembling the transceiver.
• DO NOT open the transceiver until the transceiver is disconnected from a power source.
• DO NOT force any of the variable components. Turn them slowly and smoothly.
• DO NOT short any circuits or electronic parts. An insulated tuning tool MUST be used for all adjustments.
• DO NOT apply power ON for a long time when the transceiver is defective.
• DO NOT transmit power into a signal generator or a sweep generator.
• ALWAYS connect so dB-40 dB attenuator between the transceiver and a deviation meter or spectrum analyzer when using such test equipment.
• READ the instructions of test equipment thoroughly before connecting equipment to the transceiver.
• There are different versions of this transceiver. Adjustment procedures and data may differ for each version. Please be sure to follow the procedure for the transceiver you adjust.

REQUIRED TEST EQUIPMENT:

3-1.1 POWER SUPPLY CONNECTION

Diagram shows connecting the battery terminal and chassis to the AC power supply using alligator clips.

3-1.2 SEPARATING THE RF UNIT FROM THE MAIN UNIT

Diagram illustrates separating the RF UNIT from the MAIN UNIT using two extension cable kits (573-10). These kits must be ordered from an authorized Icom Dealer.

3-2 PLL ADJUSTMENT

This section details the PLL adjustment procedure.

Diagram: The RF UNIT diagram shows the adjustment points: C75 for PLL reference frequency adjustment and C714 for Lock voltage adjustment (requires peeling off silver tape before adjusting). CP1 is indicated as the Lock voltage check point. The VCO UNIT is also shown.

3-3 RECEIVER ADJUSTMENT

This section covers receiver adjustments.

* CCW: Counterclockwise

Diagram: The RF UNIT diagram shows the S-meter adjustment at R19 and sensitivity adjustment points L1-L6. J2 pin 7 is marked as the sensitivity check point.

3-4 TRANSMITTER ADJUSTMENT

This section details transmitter adjustments.

Diagrams:

• MAIN AND TONE UNITS: Shows IC-12GAT with R68 (Output power adjustment), R241 (Frequency deviation adjustment), and R601 (Subaudible tone frequency deviation adjustment). Shows IC-12GE with R68 (Output power adjustment), R241 (Frequency deviation adjustment), and R242 (Tone call frequency deviation adjustment).
• RF UNIT: Shows the location of R68.
• DTMF UNIT: Shows the location of R801 (DTMF tone frequency deviation adjustment).

SECTION 4 BOARD LAYOUTS

4-1 LOGIC UNIT

This section provides board layouts for the Logic Units.

• LOGIC-B UNIT: Component side and foil side diagrams are provided, showing component placement and traces.
• LOGIC-A UNIT: Component side and foil side diagrams are provided, showing component placement and traces.
• SQUELCH UNIT: Diagram showing component layout.
• POWER SWITCH/VOLUME CONTROL: Diagram showing component layout.
• Component Descriptions: Detailed diagrams and symbols for various transistors (e.g., 2SA1362, 2SC4081, RN1404), diodes (e.g., 1SS184, 1SS193), and other components are provided.

4-2 MAIN UNIT

This section provides the board layout for the Main Unit.

• MAIN UNIT: A comprehensive component side diagram of the Main Unit is shown, detailing the placement of ICs, transistors, resistors, capacitors, and connectors, along with their labels and pinouts.
• Component Descriptions: Diagrams and symbols for various transistors (e.g., 2SA1162, 2SC4081, 2SB909M), diodes (e.g., 1SS184, DAP202U), and other components are provided.

4-3 RF UNIT

This section provides the board layout for the RF Unit.

• RF UNIT: A component side diagram of the RF Unit is presented, showing the arrangement of components like ICs, transistors, resistors, capacitors, and crystals, along with their reference designators.
• Component Descriptions: Diagrams and symbols for various transistors (e.g., 2SA1162, 2SC4095, 2SB909M), diodes (e.g., 1SS193, 1SS196), and other components are provided.

4-4 ATTACHED UNITS (RF UNIT)

This section details the board layouts for attached units within the RF Unit.

• VCO UNIT, IF, PLL, LPF, APC: Component side diagrams for each of these units are provided, showing component placement and traces.
• Component Descriptions: Diagrams and symbols for transistors (e.g., 2SC3356, 2SC3585, RN1403) and diodes (e.g., MA862, MA334 B) used in these units are included.

4-5 DTMF AND TONE UNITS (IC-12GAT ONLY)

This section provides board layouts for the DTMF and Tone Units.

• DTMF UNIT: Component side diagram showing component placement, including IC801, Q801, D801, X801, and various resistors and capacitors.
• TONE UNIT: Component side diagram showing component placement, including IC601, IC602, X601, and various resistors and capacitors.
• Component Descriptions: Diagrams and symbols for transistors (e.g., 2SC2712 BL) and diodes (e.g., DAP202U) used in these units are included.

SECTION 5 PARTS LIST

This section contains detailed parts lists for various units of the transceiver.

[LOGIC UNIT]

SECTION 6 VOLTAGE DIAGRAM

This section provides a voltage diagram illustrating the interconnections and voltage levels within the transceiver's main units: LOGIC UNIT, RF UNIT, and MAIN UNIT. It details signal paths and power distribution, crucial for troubleshooting and diagnostics.

COMPANY INFORMATION

Icom Inc. is headquartered in Osaka, Japan, with various international branches including Icom America Inc., Icom Canada, Icom (Europe) GmbH, Icom (Australia) Pty. Ltd., and Icom France S.a. The manual was printed in Japan in 1989.