Icom IC-T81E Service Manual
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Icom IC-T81E Service Manual

Multiband fm transceiver
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SERVICE
MANUAL
MULTIBAND FM TRANSCEIVER

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Summary of Contents for Icom IC-T81E

  • Page 1 SERVICE MANUAL MULTIBAND FM TRANSCEIVER...
  • Page 2 SYMBOL U.S.A. USA-1 IC-T81A Australia S.E.Asia Europe IC-T81E U.K. Italy 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.

  • Page 3: Table Of Contents

    TABLE OF CONTENTS SECTION SPECIFICATIONS SECTION INSIDE VIEWS SECTION DISASSEMBLY INSTRUCTIONS SECTION CIRCUIT DESCRIPTION RECEIVER CIRCUITS ........... . .4-1 TRANSMITTER CIRCUITS .
  • Page 4 SECTION 1 SPECIFICATIONS GENERAL • Frequency range Version 145 MHz 440 MHz 1200 MHz 91.5 MHz (RX only) 50 MHz TX: 144 – 148 TX: 430 – 450 U.S.A. 1240 – 1300 76 – 107.995 50 – 53.995 RX: 118 – 173.995 RX: 400 –...
  • Page 5 RECEIVER • Receiver system : Double-conversion superheterodyne • Intermediate frequency : 1st 69.45 MHz (13.35 MHz: WFM) 2nd 450 kHz • Sensitivity* (except spurious points; typical values) Band 50 MHz 0.56 µV – 0.18 µV 144 MHz 0.18 µV – –...
  • Page 6 SECTION 2 INSIDE VIEWS • LOGIC UNIT BOTTOM VIEW Crystal filter (X1: CR-639 5.039MH) (IC1: M38267M8LGP) AF mute switch (Q361: 2SJ364) AF volume (IC202: M5222FP) AF power amplifier IF IC (IC201: TA7368F) (IC701: TA31136FN) • RF UNIT BOTTOM VIEW TOP VIEW Power amplifier (Q922: 2SK3075) Drive amplifier...

  • Page 7: Disassembly Instructions

    SECTION 3 DISASSEMBLY INSTRUCTIONS • REMOVING THE CHASSIS PANEL • REMOVING THE SHIELD PLATE 1 Remove 1 knob A, and unscrew 1 nut B. 1 Unsolder 10 points, F, to separate the shield plate and 2 Unscrew 2 screws C. LOGIC unit.

  • Page 8: Circuit Description

    SECTION 4 CIRCUIT DESCRIPTION 4-1 RECEIVER CIRCUITS Thus, transmit signals are blocked from entering the receiv- er circuits. The antenna switching circuit employs a 1/4 4-1-1 DUPLEXER CIRCUIT (RF UNIT) type diode switching system. The passed signals are then The transceiver has a duplexer (low-pass and high-pass fil- applied to each RF amplifier circuit.
  • Page 9 • RF signals WFM band • 50, 144, 440 and 1200 MHz band The WFM band signals are applied to the RF amplifier The applied RF signals are mixed with 1st LO signals at the (Q201) via the tunable band-pass filter (D202). The ampli- 1st mixer (IC601) to produce a 69.45 MHz 1st IF signal.

  • Page 10: Transmitter Circuits

    4-1-8 2ND IF AND DEMODULATOR CIRCUITS Even when the squelch is closed, the AF mute switch (Q361) opens at the moment of emitting beep tones. (RF AND LOGIC UNITS) The 2nd mixer circuit converts the 1st IF signal to the 2nd IF •...
  • Page 11 The amplified signal is passed through the antenna switch- (3) 440 MHz band ing circuit (D101 and D102), low-pass filters and high-pass The signals from the limiter amplifier (RF unit; IC301) filters. The signal is applied to the antenna connector. changes the reactance of a diode (VCO unit;...

  • Page 12: Pll Circuits

    The APC sensor (R911) detects driving current from the The applied signal is divided by serial data from the CPU (N- drive voltage at the YGR (Q138), drive (Q921) and power data) and phase-detected with the divided reference fre- (Q922) amplifiers. The detected current is converted into DC quency (5 kHz) at the phase detector section in the PLL IC.

  • Page 13: Port Allocations

    4-5 PORT ALLOCATIONS 4-5-2 I/O EXPANDER IC (RF UNIT; IC3) 4-5-1 I/O EXPANDER IC (RF UNIT; IC2) Port Port Description Description number name number name Outputs VHVCO3 regulator control Outputs 300 MHz band RX regulator signal. control signal. Outputs VLVCO3 regulator control Outputs AM mode regulator control signal.
  • Page 14 4-5-3 CPU (LOGIC UNIT; IC1) Port Port Description Description number name number name Input port for the over-voltage detec- CLONEIN Input port for the cloning signal. tion from connected battery pack or Outputs T4 regulator control signal. external power supply. High : While transmitting.

  • Page 15: Adjustment Procedures

    SECTION 5 ADJUSTMENT PROCEDURES 5-1 PREPARATION ‘ ‘ REQUIRED TEST EQUIPMENT EQUIPMENT GRADE AND RANGE EQUIPMENT GRADE AND RANGE Output voltage : 13.5 V DC DC voltmeter Input impedance : 50 kΩ/V DC or better DC power supply Current capacity : 3 A or more Frequency range : 300–3000 Hz...

  • Page 16: Pll Adjustment

    5-2 PLL ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST PLL LOCK • Displayed frequency : Connect 0.8 V – 1.8 V Verify VOLTAGE 51.000 MHz voltmeter •...
  • Page 17 • RF UNIT BOTTOM VIEW 12LV PLL lock voltage check point (for 1200 MHz) PLL lock voltage check point (for 440 MHz) PLL lock voltage check point (for 50 MHz RX, WFM and 144 MHz) • RF UNIT TOP VIEW 6MLV PLL lock voltage check point (for 50 MHz TX)

  • Page 18: Receiver Adjustment

    5-3 RECEIVER ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST 50 MHz • Displayed frequency : LOGIC Connect a multime- Maximum voltage [DIAL] SENSITIVITY 50.000 MHz ter to check point panel •...
  • Page 19 • LOGIC UNIT TOP VIEW 50 MHz, WFM BAND, AIR BAND and 145 MHz Sensitivity check point 5 - 5...
  • Page 20 RECEIVER ADJUSTMENT (Continued) The following adjustment must be performed on the normal mode after “SENSITIVITY ADJUSTMENT” in SECTION 5-3. MEASUREMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION S-METER • Displayed frequency : Push and hold (50 MHz band) 51.000 MHz [EUR], [UK], [ITA] panel the [SQL] key 52.000 MHz...
  • Page 21 RECEIVER ADJUSTMENT (Continued) The SQUELCH LEVEL adjustment must be performed on the normal mode after “S-METER ADJUSTMENT”. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST S-METER • Displayed frequency : Push and hold 445.000 MHz [USA-1] panel the [SQL] key (440 MHz band) 435.000 MHz [other]...

  • Page 22: Transmitter Adjustment

    5-4 TRANSMITTER ADJUSTMENT The following adjustment must be performed at “ADJUSTMENT MODE”. MEASUREMENT ADJUSTMENT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION OUTPUT • Displayed frequency : Connect more than 5 W [DIAL] POWER 51.000 MHz [EUR], [UK], [ITA] panel power meter to the 52.000 MHz antenna connector.
  • Page 23 TRANSMITTER ADJUSTMENT (Continued) The following adjustment must be performed after “REFERENCE FREQUENCY ADJUSTMENT” in SECTION 5-2. ADJUSTMENT MEASUREMENT POINT ADJUSTMENT ADJUSTMENT CONDITION VALUE UNIT LOCATION UNIT ADJUST • Displayed frequency : Connect 4.5 kHz LOGIC R327 DEVIATION 51.000 MHz [EUR], [UK], [ITA] panel deviation meter to (50 MHz)

  • Page 24: Logic Unit

    SECTION 6 PARTS LIST [LOGIC UNIT] [LOGIC UNIT] ORDER ORDER DESCRIPTION DESCRIPTION 1140008110 S.IC M38267E8GP [USA-1] only 6200006720 S.COIL 5CA-395KN-0369AQ=P3 1140008100 S.IC M38267M8L-230GP [other] 6200003550 S.COIL MLF1608A 4R7K-T 1130009160 S.IC X24320S8I-2.5T4 6200001820 S.COIL LQH 3N 331K 04 1110004890 S.IC XC6371A500PR L702 6150005010 S.COIL LS-528 (637AN-0223GW=P3)
  • Page 25 [LOGIC UNIT] [LOGIC UNIT] ORDER ORDER DESCRIPTION DESCRIPTION R245 7030005080 S.RESISTOR ERJ2GEJ 823 X (82 kΩ) R757 7030005220 S.RESISTOR ERJ2GEJ 223 X (22 kΩ) R246 7030005310 S.RESISTOR ERJ2GEJ 124 X (120 kΩ) R758 7030005240 S.RESISTOR ERJ2GEJ 473 X (47 kΩ) R247 7030005090 S.RESISTOR ERJ2GEJ 104 X (100 kΩ)

  • Page 26: Rf Unit

    [LOGIC UNIT] [LOGIC UNIT] ORDER ORDER DESCRIPTION DESCRIPTION C307 4030013850 S.CERAMIC ECUE1E102KBQ 2260002530 S.SWITCH EVQ-WRR001 C308 4030014500 S.CERAMIC ECUE1H121JCQ S401 2230000900 S.SWITCH JPM1990-2013R C309 4030009000 S.CERAMIC C2012 JB 1C 224K-T-A S402 2230000900 S.SWITCH JPM1990-2013R C310 4030014220 S.CERAMIC ECUE1E471KBQ C311 4550005980 S.TANTALUM TEMSVA 1A 475M-8L C312 4030014220 S.CERAMIC...
  • Page 27 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION Q826 1590001910 S.TRANSISTOR UN911D (TX) D803 1790001260 S.DIODE MA2S077-(TX) Q827 1590001970 S.TRANSISTOR UN921E (TX) D804 1790001260 S.DIODE MA2S077-(TX) Q828 1590001910 S.TRANSISTOR UN911D (TX) D805 1790001260 S.DIODE MA2S077-(TX) Q829 1590001970 S.TRANSISTOR UN921E (TX) D806 1790001260 S.DIODE MA2S077-(TX)
  • Page 28 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION L143 6200006770 S.COIL ELJRE 1N5Z-F 7030005220 S.RESISTOR ERJ2GEJ 223 X (22 kΩ) L201 6200008730 S.COIL ELJND R10J 0.1U 7030005220 S.RESISTOR ERJ2GEJ 223 X (22 kΩ) L202 6200008730 S.COIL ELJND R10J 0.1U 7030007300 S.RESISTOR ERJ2GEJ 332 X (3.3 kΩ) L205 6200008730 S.COIL...
  • Page 29 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION ERJ2GEJ 150 X (15 Ω) ERJ2GEJ 561 X (560 Ω) R351 7030005300 S.RESISTOR R857 7030008370 S.RESISTOR R401 7030007300 S.RESISTOR ERJ2GEJ 332 X (3.3 kΩ) R862 7030005290 S.RESISTOR ERJ2GEJ 682 X (6.8 kΩ) ERJ2GEJ 101 X (100 Ω) R402 7030005120 S.RESISTOR...
  • Page 30 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION 4030014090 S.CERAMIC ECUE1H060CCQ C120 4030016820 S.CERAMIC ECUE1HR75BCQ 4030014170 S.CERAMIC ECUE1H330JCQ C121 4030013850 S.CERAMIC ECUE1E102KBQ 4030014120 S.CERAMIC ECUE1H100CCQ C123 4030014120 S.CERAMIC ECUE1H100CCQ 4030014420 S.CERAMIC ECUE1H0R5BCQ C124 4030013850 S.CERAMIC ECUE1E102KBQ 4030014090 S.CERAMIC ECUE1H060CCQ C131 4030013850 S.CERAMIC ECUE1E102KBQ 4030014100 S.CERAMIC...
  • Page 31 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION C321 4030014180 S.CERAMIC ECUE1H470JCQ C728 4030014100 S.CERAMIC ECUE1H070CCQ C322 4030013850 S.CERAMIC ECUE1E102KBQ C729 4030014020 S.CERAMIC ECUE1H020BCQ C323 4030014020 S.CERAMIC ECUE1H020BCQ C730 4030009820 S.CERAMIC C1005 JB 1C 103K-T-A C324 4030013850 S.CERAMIC ECUE1E102KBQ C731 4030009820 S.CERAMIC C1005 JB 1C 103K-T-A C325...
  • Page 32 [RF UNIT] [RF UNIT] ORDER ORDER DESCRIPTION DESCRIPTION C895 4030013850 S.CERAMIC ECUE1E102KBQ C991 4030014200 S.CERAMIC ECUE1H101JCQ C896 4030014050 S.CERAMIC ECUE1H030BCQ C992 4030014200 S.CERAMIC ECUE1H101JCQ C897 4030014090 S.CERAMIC ECUE1H060CCQ C993 4030013850 S.CERAMIC ECUE1E102KBQ C898 4030013850 S.CERAMIC ECUE1E102KBQ C994 4030014200 S.CERAMIC ECUE1H101JCQ C899 4030013850 S.CERAMIC ECUE1E102KBQ...
  • Page 33 [VCO BOARD] [VCO BOARD] ORDER ORDER DESCRIPTION DESCRIPTION R314 7030005290 S.RESISTOR ERJ2GEJ 682 X (6.8 kΩ) C376 4030014070 S.CERAMIC ECUE1H040BCQ ERJ2GEJ 101 X (100 Ω) R315 7030004980 S.RESISTOR C377 4030014110 S.CERAMIC ECUE1H080CCQ ERJ2GEJ 221 X (220 Ω) R316 7030004990 S.RESISTOR C378 4030014000 S.CERAMIC ECUE1H1R5BCQ...
  • Page 34 SECTION 7 MECHANICAL PARTS AND DISASSEMBLY [CHASSIS PARTS] [VCO UNIT] REF. NO. ODER NO. DESCRIPTION QTY. REF. NO. ODER NO. DESCRIPTION QTY. 8510012100 2135 VCO case 6510020650 Connector SMA-R224 7600000210 Encoder TP70N00E20-15F-1903 [ACCESSORIES] 2510000960 Speaker CS028014-12 REF. NO. ODER NO. DESCRIPTION QTY.
  • Page 35 MP13 (C) MP30 (C) MP10 (C) MP24 (C) J1 (C) MP21 (C) MP31 (C) S1 (C) RF unit MP1 (RF) MP28 (C) MP29 (C) MP6 (L) MP9 (L) MP29 (C) MP29 (C) MP2 (C) MP14 (C) MP5 (L) MP2 (L) MP1 (L) MP4 (L) MP17 (C)
  • Page 36 SECTION 8 SEMI-CONDUCTOR INFORMATION • • TRANSISTOR AND FET’S DIODES 2SA1588 GR 2SB1132 R 2SB1201 S 2SB1462 R 2SC3356 R25 1SS364 1SV270 1SV271 1SV282 1SV288 (Symbol: ZG) (Symbol: BARB) (Symbol: B1201) (Symbol: BR) (Symbol: R25) (Symbol: BF) (Symbol: TF) (Symbol: TG) (Symbol: TD) (Symbol: TJ) pink...
  • Page 37 SECTION 9 BOARD LAYOUTS 9-1 LOGIC UNIT • TOP VIEW R141 R214 R213 C102 C246 R248 R153 R247 C321 R246 R329 R154 C927 C322 R330 R322 C240 C328 R339 R244 C320 R241 R328 C241 R242 C326 R305 R757 C756 C757 R758 R760 Q752...
  • Page 38 • BOTTOM VIEW C202 R202 C203 C204 R148 R142 C210 C919 C213 C215 C201 IC202 Q201 C217 R215 C214 R333 Q308 R207 C917 C361 C325 C162 R196 R253 R342 R361 R362 R208 R335 R318 R343 C248 Q307 C318 C313 R250 R211 C309 IC141...
  • Page 39 9-2 RF UNIT • TOP VIEW C741 C170 D134 R163 C960 C914 L916 C172 L142 Q922 R949 R928 C948 L917 C198 C199 C949 C869 Q923 R924 R930 C928 C950 C969 L912 R932 C867 C951 Q912 C137 L123 C981 L933 C964 R931 L906 L801...
  • Page 40 • BOTTOM VIEW R721 C726 R140 L726 C149 R144 L136 C192 R881 R138 C141 C879 C728 R882 C171 C173 R139 L721 C722 Q140 R134 C160 Q139 C196 C729 R157 C163 R742 R725 R160 D141 Q721 C877 R888 R152 L723 C731 C886 C157 R727...

  • Page 41: Vco Board

    9-3 VCO BOARD • TOP VIEW J302 to RF unit R330 R319 R327 C374 R328 C310 C319 Q351 Q323 C308 R312 Q313 C372 R367 C316 R307 C328 C368 R315 R366 C373 C307 R326 C389 C317 R363 C361 C315 C371 R313 R305 R369 C313...
  • Page 42 • BOTTOM VIEW C388 Q354 R374 Q353 L333 R371 L337 C378 C380 C381 C384 L336 9 - 6...

  • Page 43: Logic Unit

    SECTION 10 BLOCK DIAGRAM LOGIC UNIT RF UNIT PSET VCO BOARD Q350: 2SC5006 D806: MA2S077 D351: 1SV270 Q824: 2SC5195 D807: MA2S077 Q131: 2SC5195 Q132: 2SC5454 D352: MA2S077 BAND SW TX/RX BUFF BUFF BUFF BUFF 50MHz DC-DC DC-DC Q306: 2SJ364 Q353: 2SC5195 Q354: RX-Lo FREQUENCY: TX-Lo FREQUENCY:...
  • Page 44 RF UNIT TX/RX FREQUENCY D806: MA2S077 D51: MA2S077 Q138: MXR9745 Q824: 2SC5195 D807: MA2S077 Q131: 2SC5195 Q132: 2SC5454 D52: MA2S077 TX/RX TX FREQUENCY: 1200MHz BAND BUFF BUFF RX-Lo FREQUENCY: TX-Lo FREQUENCY: 1200MHz BAND 1200MHz BAND TX FREQUENCY: D804: MA2S077 Q136: D402: MA2S077 430MHz BAND 2SC3356...
  • Page 45 SECTION 10 BLOCK DIAGRAM LOGIC UNIT RF UNIT PSET TX/RX FREQUENCY VCO BOARD Q350: 2SC5006 D806: MA2S077 D51: MA2S077 D351: 1SV270 Q131: 2SC5195 Q132: 2SC5454 Q138: MXR9745 Q824: 2SC5195 D807: MA2S077 D52: MA2S077 D352: MA2S077 TX FREQUENCY: 1200MHz BAND BAND SW BUFF BUFF TX/RX...
  • Page 46 SECTION 11 VOLTAGE DIAGRAM 11-1 LOGIC UNIT C: 13.5 CPUHV T: 0 D141 C103 R: 3.4 MA2S111 198nS 0.001 R756 R151 C718 Q151 LM-1782B D151 R153 C719 2SD2216 S C737 MA8100 M R141 47 K Q753 0.01 15 K UN9115 C102 D152 R719...
  • Page 47 NTCCF20124AH 473KCT T: 0 R: 3.4 C737 0.01 2NDLO 100K C907 0.001 R717 C709 C708 C707 C706 R726 0.01 47 K C703 0.001 TC4W53FU OSCIN MIXIN OSCOUT THERMC C906 MIXOUT N-REC 0.001 N-DET IFIN RSSI IFOUT C700 2NDLO 2NDLO R737 FILOUT QUAD IFIN...
  • Page 48 SECTION 11 VOLTAGE DIAGRAM 11-1 LOGIC UNIT C: 13.5 NTCCF20124AH 473KCT CPUHV D141 T: 0 C103 R: 3.4 198nS MA2S111 R151 0.001 R756 C718 Q151 LM-1782B R153 D151 C719 2SD2216 S MA8100 M C737 47 K R141 Q753 0.01 15 K 2NDLO C102 D152...

  • Page 49: Rf Unit

    11-2 RF UNIT 50T:3.1 50R:0.4 R874 C863 R341 C342 10 K 0.22 390 K 0.001 C344 0.001 6MVCO3 C862 R342 R343 0.001 2.7 K Q341 R344 56 K 2SC4215-O 50T:0.6 50T:2.2 50R:0.4 50T:0.8 50R:0.5 D341 R802 50R:0.4 1SV288 R881 R349 R865 100 K C805...
  • Page 50 D142 MA2S111 50TX UHFTX C183 VHFTX 0.001 C150 R138 R140 D143 C144 0.001 Q929 R144 MA2S111 R953 0.01 3.9 K R934 4.7 K 2SA1588 GR 50T:2.2 R135 L134 R142 R141 L135 Q928 50T:0.8 50R:0.5 C182 0.82 3.9 K 0.18 H 50R:0.4 0.001 UN9211...
  • Page 51 11-2 RF UNIT 50T:3.1 R341 50R:0.4 D142 R874 C863 C342 10 K 0.22 390 K 0.001 C344 MA2S111 50TX UHFTX 0.001 6MVCO3 C183 C862 VHFTX R342 R343 0.001 C150 0.001 D143 R138 R140 0.001 2.7 K R344 Q341 C144 R144 Q929 MA2S111 0.01...
  • Page 52 Fax : ( 604 ) 952-0090 Icom (UK) Ltd. : http://www.icomcanada.com Unit 9, Sea St., Herne Bay, Kent, CT6 8LD, U.K. Icom (Australia) Pty. Ltd. Phone : 01227 741741 Fax : 01227 741742 A.B.N. 88 006 092 575 : http://www.icomuk.co.uk 290-294 Albert Street, Brunswick, Victoria, 3056, Australia Icom France S.a...
  • Page 53 A-5566I-S-1 1-1-32, Kamiminami, Hirano-ku, Osaka, 547-0003, Japan © 1999 Icom Inc.

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