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Icom Ic-t81 Service Manual Pages

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SERVICE MANUAL MULTIBAND FM TRANSCEIVER INTRODUCTION This service manual describes the latest service information for the IC-T81A/E at the time of publication. MODEL VERSION U.S.A. Australia S.E.Asia Europe U.K. Italy IC-T81A IC-T81E SYMBOL USA-1 AUS SEA EUR UK ITA To upgrade quality, all electrical or mechanical parts and internal circuits are subject to change without notice or obligation. DANGER NEVER connect the transceiver to an AC outlet or to a DC power supply that uses more than 16 V. Such a connection could cause a fire hazard and/or electric. DO NOT expose the transceiver to rain, snow or any liquids. DO NOT reverse the polarities of the power supply when connecting the transceiver. om DO NOT apply an RF signal of more than 20 dBm (100mW) to the antenna connector. This could damage the transceiver's front end. l.c ORDERING PARTS pa irm 10-digit order numbers Component part number and name Equipment model name and unit name Quantity required re 1. 2. 3. 4. an ua Be sure to include the following four points when ordering replacement parts: ic e- 1 pieces 10 pieces se rv 1130009370 S.IC TB31242FN IC-T81A/E RF UNIT 8810008990 Screw PH BT M2x10 ZK IC-T81A/E Chassis Addresses are provided on the inside back cover for your convenience. REPAIR NOTES 1. 2. 3. 4. 5. 6. 7. Make sure a problem is internal before disassembling the transceiver. DO NOT open the transceiver until the transceiver is disconnected from its 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 turning tool MUST be used for all adjustments. DO NOT keep 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 a 40 dB to 50 dB attenuator between the transceiver and a deviation meter or spectrum analyzer when using such test equipment. 8. READ the instructions of test equipment thoroughly before connecting equipment to the transceiver. TABLE OF CONTENTS SECTION 1 SPECIFICATIONS SECTION 2 INSIDE VIEWS SECTION 3 DISASSEMBLY INSTRUCTIONS SECTION 4 CIRCUIT DESCRIPTION RECEIVER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1 4-2 TRANSMITTER CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3 4-3 PLL CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5 POWER SUPPLY CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5 4-5 PORT ALLOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6 l.c ADJUSTMENT PROCEDURES an ua 5 om 4-4 PREPARATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1 5-2 PLL ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2 5-3 RECEIVER ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4 5-4 TRANSMITTER ADJUSTMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8 6 PARTS LIST SECTION 7 MECHANICAL PARTS AND DISASSEMBLY SECTION 8 SEMI-CONDUCTOR INFORMATION SECTION 9 BOARD LAYOUTS SECTION SECTION se rv SECTION ere pa irm 5-1 ic SECTION 4-1 9-1 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-1 9-2 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3 9-3 VCO BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-5 10 BLOCK DIAGRAM 11 VOLTAGE DIAGRAM 11-1 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1 11-2 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-2