Table of Contents

		TABLE OF CONTENTS
SECTION	1	SPECIFICATIONS
SECTION	2	INSIDE VIEWS
SECTION	3	DISASSEMBLY INSTRUCTIONS
SECTION	4	CIRCUIT DESCRIPTION
	4-1	RECEIVER CIRCUITS	.4-1
	4-2	TRANSMITTER CIRCUITS	.4-3
	4-3	PLL CIRCUITS	.4-5
	4-4	POWER SUPPLY CIRCUITS	.4-5
	4-5	PORT ALLOCATIONS	.4-6
SECTION	5	ADJUSTMENT PROCEDURES
	5-1	PREPARATION	.5-1
	5-2	PLL ADJUSTMENT	.5-2
	5-3	RECEIVER ADJUSTMENT	.5-4
	5-4	TRANSMITTER ADJUSTMENT	.5-8
SECTION	6	PARTS LIST
SECTION	7	MECHANICAL PARTS AND DISASSEMBLY
SECTION	8	SEMI-CONDUCTOR INFORMATION
SECTION	9	BOARD LAYOUTS
	9-1	LOGIC UNIT	.9-1
	9-2	RF UNIT	.9-3
	9-3	VCO BOARD	.9-5

SECTION 10 BLOCK DIAGRAM

SECTION 11 VOLTAGE DIAGRAM

11-1 LOGIC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-1 11-2 RF UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-2

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Contents

Multiband FM Transceiver Sample Order IntroductionOrdering Parts Repair Notes Table of Contents Version 50 MHz 145 MHz 440 MHz 1200 MHz MHz RX only SpecificationsGeneral Transmitter WFM ReceiverBand WFM CPU Inside ViewsLogic Unit RF Unit Logic unit Disassembly InstructionsRemoving the Chassis Panel Removing the Shield Plate Removing the Logic Unit Removing the RF Unit Duplexer Circuit RF Unit Antenna Switching Circuits RF UnitCircuit Description Receiver Circuits 7 1ST Mixer Circuit RF Unit Transmitter Circuits APC Control Circuit DRIVE/POWER Amplifier Circuits RF UnitAPC Circuits RF Unit MHz PA VCC Power Supply Circuits Voltage LinePLL Circuits Line Description Pin Port Description Number Name Port Allocations1 I/O Expander IC RF Unit IC2 2 I/O Expander IC RF Unit IC3 CPU Logic Unit IC1 Connection Adjustment ProceduresPreparation ‘ Required Test Equipment PLL Adjustment RF Unit TOP View 6MLV RF Unit Bottom ViewULV VLV VHF Receiver AdjustmentDial Sensitivity Logic Unit TOP View 101 dBm MeterSSG Top Push and hold MHz band SQL key Displayed frequencyPush and hold 445.000 MHz USA-1 Transmitter Adjustment AUS, SEA DeviationHPF OFF LPF Dtmf =Surface mount Parts List Trimmer Ceramic ECUE1H121JCQ Transistor UN911D TX Coil Eljnd R10J 0.1U Themistor Ceramic ECUE1H060CCQ Ceramic ECUE1H390JCQ VCO Board Ceramic ECUE1H120JCQ VCO Unit Mechanical Parts and DisassemblyAccessories Chassis Parts MP29 C SEMI-CONDUCTOR Information Transistor and FET’SDiodes Board Layouts Logic UnitTOP View GND Pset Ifin Bottom ViewIC1 IC3 J4 to Logic unit J1 RF UnitIC6 L912 MP1 IC3IC2 VLVCO3 VHF GND VHVCO3 UVCO3 Uhfout GND 12VCO3 GND VCO BoardJ302 to RF unit OUT 12VCOOUT Q354 Block Diagram ANT LPF HPF AMP Mode Xtal BPF PDA2, CK AMPTX/RX Frequency TX/RX Buff ANT Buff HPF LPF YGR ResetMode Xtal Initial BPF MOD TX/RX Frequency Logic Unit Section Voltage Diagram WFM NTCCF20124AH 473KCT TXC 2NDLOOscin Mixin Oscout GND Mixout REC VCC DET Ifin Rssi DEC Ifout Filout Quad COM4 COM3 COM2 COM1 12VCO COM2 ResetCOM3 COM2 Reset Power Clonein VCC VIN Cpuhv 1200M RF UnitVHF 400M 400MHz 50M00M 1200MHz LOK GND2 GND1PLST1 IN1 ENB VCC2 Icom America Inc Icom Inc 5566I-S

Motorola IC-T81E, IC-T81A service manual Table of Contents

Models: IC-T81E IC-T81A