Kenwood TM-281A Service Manual
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Kenwood TM-281A Service Manual

144mhz
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144MHz FM TRANSCEIVER
TM-281A
SERVICE MANUAL
Knob (VOL)
(K29-9498-03)
Modular jack (MIC)
(E58-0535-05)
DISASSEMBLY FOR REPAIR ......................2
CIRCUIT DESCRIPTION ..............................5
COMPONENTS DESCRIPTION ...................9
SEMICONDUCTOR DATA .........................11
PARTS LIST ...............................................12
EXPLODED VIEW ......................................18
PACKING ....................................................19
ADJUSTMENT ..........................................20
RoHS
This product complies with the
Key top
(K29-9497-01)
CONTENTS
directive for the European market.
© 2011-8 PRINTED IN JA PAN
B51-8988-00 ( N ) 217
Knob (ENC)
Panel assy
(K29-9499-03)
(A62-1187-13)
TERMINAL FUNCTION .............................29
TX-RX UNIT (X57-8130-XX) ..................30
SCHEMATIC DIAGRAM ............................36
BLOCK DIAGRAM .....................................40
LEVEL DIAGRAM ......................................42
SPECIFICATIONS ...................BACK COVER
This product uses Lead Free solder.

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  • Page 1: Table Of Contents

    144MHz FM TRANSCEIVER TM-281A SERVICE MANUAL © 2011-8 PRINTED IN JA PAN B51-8988-00 ( N ) 217 Knob (VOL) Knob (ENC) Panel assy (K29-9498-03) (K29-9499-03) (A62-1187-13) Modular jack (MIC) Key top (E58-0535-05) (K29-9497-01) CONTENTS DISASSEMBLY FOR REPAIR ......2 TERMINAL FUNCTION ......29 CIRCUIT DESCRIPTION ......5...

  • Page 2: Disassembly For Repair

    Kenwood reserves the right to make changes to any wise, for any purpose without the prior written permission products herein at any time for improvement purposes.
  • Page 3 TM-281A DISASSEMBLY FOR REPAIR 3. Disconnect the fl at cable from the connector of the panel 5. When removing the TX-RX PCB, fi rst remove the solder assembly. of the antenna hot pin and positive terminal of the DC cord.
  • Page 4 TM-281A DISASSEMBLY FOR REPAIR 6. Pull it out behind the chassis by rotating the bush e of 2. When mounting the panel assembly, pass the fl at cable the DC cord 90 degrees in the direction of the arrow after...

  • Page 5: Circuit Description

    TM-281A CIRCUIT DESCRIPTION ■ IF Amplifi er Frequency Confi guration The fi rst IF signal is amplifi ed by Q503, and then goes to The receiver utilizes double conversion. The first IF is IC501 (FM processing IC). The signal is heterodyned again 49.95MHz and the second IF is 450kHz.
  • Page 6 TM-281A CIRCUIT DESCRIPTION ■ Wide/Narrow Switching Circuit ■ Squelch Circuit The Wide port (pin 65) and Narrow port (pin 64) of the The detection output from the FM IC (IC501) passes MCU is used to switch between ceramic filters. When through a noise amplifier (Q502) to detect noise.
  • Page 7 TM-281A CIRCUIT DESCRIPTION ■ Unlock Circuit Transmitter System During reception, the 8RC signal goes high, the 8TC ■ Outline signal goes low, and Q708 turns on. Q710 turns on and a The transmitter circuit produces and amplifi es the desired voltage is applied to 8R.
  • Page 8 TM-281A CIRCUIT DESCRIPTION ■ Key Matrix Circuit Control Circuit The front panel has function keys. Each of them is con- The MCU carries out the following tasks (See Fig. 10.): nected to a cross point of a matrix of the KI1 to KI3 and KSI 1) Controls the WIDE, NARROW, and TX/RX outputs.

  • Page 9: Components Description

    TM-281A CIRCUIT DESCRIPTION ■ D/A Converter on MCU port 18 (INT) if B line becomes less than approxi- mately 9.5V. The MCU will then send the backup data to the The D/A converter (IC705) is used to adjust the MO mod- EEPROM (IC708) and enter stop mode.
  • Page 10 TM-281A COMPONENTS DESCRIPTION Ref. No. Use / Function Operation / Condition / Compatibility Ref. No. Use / Function Operation / Condition / Compatibility Oscillator RX VCO VCO frequency control T/R switch On when RX VCO frequency Oscillator TX VCO control...

  • Page 11: Semiconductor Data

    TM-281A SEMICONDUCTOR DATA MCU: 30622MEP540GU (TX-RX unit IC707) Pin No. Name Function Pin No. Name Function TONE CTCSS/DCS output Common data DTMF DTMF/BEEP/1750Hz output Common clock PLLE PLL IC chip select Not used Not used DST1 Destination 1 57~59 DST2~DST4...

  • Page 12: Parts List

    TM-281A PARTS LIST ✽ New Parts. indicates safety critical components. L : Scandinavia K : USA P : Canada Parts without Parts No. are not supplied. Y : PX (Far East, Hawaii) T : England E : Eu rope Les articles non mentionnes dans le Parts No. ne sont pas fournis.
  • Page 13 TM-281A PARTS LIST TX-RX UNIT (X57-8130-XX) Desti- Desti- Ref. No. Ad dress Parts No. Description Ref. No. Ad dress Parts No. Description parts nation parts nation C342 CC73HCH1H101J CHIP C 100PF C538 CK73HB1H103K CHIP C 0.010UF C343 CK73HB1H102K CHIP C...
  • Page 14 TM-281A PARTS LIST TX-RX UNIT (X57-8130-XX) Desti- Desti- Ref. No. Ad dress Parts No. Description Ref. No. Ad dress Parts No. Description parts nation parts nation C744 CK73FB1A106K CHIP C 10UF C828 CK73HB1H102K CHIP C 1000PF C745 CC73HCH1H390J CHIP C...
  • Page 15 TM-281A PARTS LIST TX-RX UNIT (X57-8130-XX) Desti- Desti- Ref. No. Ad dress Parts No. Description Ref. No. Ad dress Parts No. Description parts nation parts nation L317 L34-1039-05 AIR-CORE COIL (1.5T) R336 RK73HB1J470J CHIP R 1/16W L318-320 L34-4903-05 AIR-CORE COIL (5T)
  • Page 16 TM-281A PARTS LIST TX-RX UNIT (X57-8130-XX) Desti- Desti- Ref. No. Ad dress Parts No. Description Ref. No. Ad dress Parts No. Description parts nation parts nation R557 RK73HB1J104J CHIP R 100K 1/16W R771 RK73HB1J473J CHIP R 1/16W R558 RK73HB1J473J CHIP R...
  • Page 17 TM-281A PARTS LIST TX-RX UNIT (X57-8130-XX) Desti- Desti- Ref. No. Ad dress Parts No. Description Ref. No. Ad dress Parts No. Description parts nation parts nation R844 RK73HB1J103J CHIP R 1/16W IC710 XC6209B502P-G MOS-IC R901 RK73HB1J000J CHIP R 1/16W IC711 ✽...

  • Page 18: Exploded View

    TM-281A EXPLODED VIEW A : N35-2604-43 B : N67-3008-48 C : N80-2008-48 D : N87-2608-48 IC302 IC715 TX-RX unit (A/2) TX-RX section R380 X57 A/2 X57 A/2 J701 TX-RX unit (B/2) Display section Parts with the exploded numbers larger than 700 are not supplied.

  • Page 19: Packing

    TM-281A PACKING 713 Protection bag K,M3,M4 22 Packing fixture (H12-4330-02) 37 Microphone (T91-0624-65): M2 (T91-0641-75): K,M3,M4 710 Protection bag 23 Packing fixture 18 Fuse (Blade type) 15A (H12-4331-02) (F52-0024-05) 26 Holder (MIC) 14 DC cord (J19-1584-15) (E30-7744-05) 34 Screw set...

  • Page 20: Adjustment

    TM-281A ADJUSTMENT Measuring Equipment for Alignment Preparation 1. Digital voltmeter (DVM) • Set the controls and switches to the positions listed be- low unless otherwise specifi ed. Input impedance: High Volume control : Fully counterclockwise 2. RF voltmeter (RF VM) Power switch : OFF Input impedance: 1MΩ...
  • Page 21 TM-281A ADJUSTMENT ■ Panel Key Operation Method in Adjustment Mode Adjustment Mode This mode is used to replace or readjust the EEPROM (IC708). In Adjustment Mode, the transceiver can be adjusted us- ing its panel keys. ■ Items that can be adjusted in Adjustment Mode 1.
  • Page 22 TM-281A ADJUSTMENT Adjustment Transmit Receive Adjustment Item Display Note Signaling Frequency Point (MHz) (MHz) Frequency Tune Center 155.100 155.050 136.100 136.050 Low’ 142.100 142.050 TX High Power Center “H” icon appear 150.100 150.050 High’ 156.100 156.050 High 173.900 173.950 136.100 136.050...
  • Page 23 TM-281A ADJUSTMENT Adjustment Points Mkr1 136.1 MHz Ref –10 dBm Atten 5 dB –24.78 dBm Peak Center TX-RX UNIT (X57-8130-XX) (A/2) 136.0500000 MHz : TX-RX section Component side W1 S2 S3 FC Center 136.1 MHz Span 200 MHz #Res BW 100 kHz...
  • Page 24 TM-281A ADJUSTMENT Common Section Measurement Adjustment Item Condition Specifi cations / Remarks Test- Unit Terminal Unit Parts Method equipment 1. Setting 1) Power supply voltage DC power supply terminal : 13.8V 2. All LCD 1) All LCD segments light check Confi...
  • Page 25 TM-281A ADJUSTMENT Measurement Adjustment Item Condition Specifi cations / Remarks Test- Unit Terminal Unit Parts Method equipment 3. Low power 1) Adj item: [LPL .] Power Rear Front Tuning Write 25W±1W [Low] Adjust: [✳✳] meter panel panel control 2) Transmit [Low’]...
  • Page 26 TM-281A ADJUSTMENT Measurement Adjustment Item Condition Specifi cations / Remarks Test- Unit Terminal Unit Parts Method equipment 6. MIC sensi- 1) Frequency: 155.100MHz Linear Rear Check ±1.2~1.9kHz tivity AG: 1kHz/5.4mV K,M2,M3 detector panel (Narrow) AG: 1kHz/2.4mV M4 Oscilloscope Detector: P-P/2...
  • Page 27 TM-281A ADJUSTMENT Receiver Section (Refer to the Table 1 on page 22 for the frequencies which will apply in the adjustment mode.) Measurement Adjustment Item Condition Specifi cations / Remarks Test- Unit Terminal Unit Parts Method equipment 1. Band Pass 1) Adj item: [BPL.]...
  • Page 28 TM-281A ADJUSTMENT Measurement Adjustment Item Condition Specifi cations / Remarks Test- Unit Terminal Unit Parts Method equipment 3. Squelch 1) Adj item: [SQOL.] Rear Front Tuning Write Open 2) SSG output Oscilloscope panel panel control : –124dBm (0.14µV) • Wide...

  • Page 29: Terminal Function

    TM-281A TERMINAL FUNCTION TX-RX unit (X57-8130-XX A/2) TX-RX unit (X57-8130-XX B/2) : TX-RX Section : Display Section Pin No. Name Function Pin No. Name Function CN702 CN901 SPGND AF GND SPGND AF GND SPGND AF GND SPGND AF GND SPOUT...

  • Page 30: Pc Board

    TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 A/2) F701 C826 R821 R820 C828 C833 Q713 R336 C338 Q707 D712 D710 C815 TEMP1 R828 R762 IC712 R756...
  • Page 31 TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 A/2) Ref. No. Address IC302 IC303 IC707 IC302 IC708 IC711 IC712 IC715 C418 Q502 11N C417 Q506 Q702 D313...
  • Page 32 TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 Foil side view (J79-0316-09 A/2) R380 C421 L316 C823 TH702 C415 L319 C413 C410 C340 C404 C365 L318 D309 C399 C397 C400 D311...
  • Page 33 TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 Foil side view (J79-0316-09 A/2) Ref. No. Address J701 EXT. SP IC501 IC703 IC704 IC705 IC706 D714 IC709 IC710 R831 IC713 IC714 C847...
  • Page 34 TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (B/2): DISPLAY SECTION -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 B/2) VR901 HOOK J901 CALL TX-RX UNIT (X57-8130-XX) (B/2): DISPLAY SECTION -10: K -21: M2 -22: M3 -23: M4...
  • Page 35 TM-281A PC BOARD TX-RX UNIT (X57-8130-XX) (B/2): DISPLAY SECTION -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 B/2) J79-0316-09 B/2 Ref. No. Address S901 D903 ENCODER D904 D905 D906 D907 D908 D909 D910 D911 Component side...

  • Page 36: Schematic Diagram

    TM-281A SCHEMATIC DIAGRAM TX-RX UNIT (X57-8130-XX)(A/2) : TX-RX SECTION RX VCO Q1,2 D3,5 R:0.73V SWITCHING BUFFER AMP OSCILLATOR T:0.72V R:6.03V FREQENCY 4.5p CONTROL R:5.85V R:1.07V 2SC5108(Y)F 8.2k HZU5ALL MCH3914(7)-H 2SA1832(GR)F VOLTAGE 270n 2.7k 1.5k HVC359 0.3p DROPPED 2SC4738(GR)F R:6.91V T/R SWITCH...
  • Page 37 TM-281A SCHEMATIC DIAGRAM TX-RX UNIT (X57-8130-XX)(A/2): TX-RX SECTION R:5.00V X57-8130-XX R766 R767 R768 D9,10 R:4.82V RF AMP RF SWITCH T:5.55V T:4.76V R:5.96V HSC277 R:2.51V R307 C308 L302 L305 VCC1 VCC2 2SC5108(Y)F 1200p R:5.59V R:1.81V 1000p D10 HSC277 R528 R532 C546...
  • Page 38 TM-281A SCHEMATIC DIAGRAM IC302 RA60H1317M231 POWER MODULE TX-RX UNIT (X57-8130-XX)(A/2): TX-RX SECTION 65W:4.29V T:7.67V 25W:3.43V D306,307 DRIVE AMP D306 ANT SWITCH Q303 L407CDB C413 C420 C405 RD00HVS1-T113 T:2.71V 1000p D307 R350 STRIP LINE C406 L317 L407CDB L319 L320 R380 L308...
  • Page 39 TM-281A SCHEMATIC DIAGRAM TX-RX UNIT (X57-8130-XX)(B/2) : DISPLAY SECTION INT SP SPOUT SPGND CALL ENCODER S901 D901 W02-3704-05 REVERSE C901 Func CONNECTION PROTECTIOM 0.1u D901 R901 1SS355 R902 4.7k SEG27 SURGE 7.56V SEG26 J901 ABSORPTION SEG25 R903 HOOK SEG24 4.7k...

  • Page 40: Block Diagram

    TM-281A BLOCK DIAGRAM TX-RX UNIT (X57-8130-XX B/2): Display section TX-RX UNIT (X57-8130-XX A/2): TX-RX section 2SC4649(N,P) MB15A02PFV2E1 PLLE PLL IC MCH3914 16.8MHz 2SA1832(GR)F CHARGE TCXO PUMP TCXOMOD 2SC4738(GR)F 16.8MHz MICKEY VR901 POWER R31-0662-05 PTT/TXD L77-1944-05 LOOP VARIABLE RESISTOR FILTER IC705(5/8) CONV.
  • Page 41 TM-281A BLOCK DIAGRAM RX: 136.000~173.9975MHz (K,M2,M3) D306,D307 144.000~147.9975MHz (M4) L407CDB TX: 136.000~173.9975MHz (M2,M3) Q303 IC302 D9,D10 D309,D311 144.000~147.9975MHz (K,M4) RD00HVS1-T113 RA60H1317M231 2SC5108(Y)F UPB1509GV 2SC5108(Y)F HSC277 JDP2S12CR MCH3914(7)-H POWER TX/RX BUFF DRIVE COMM ANT SW MODULE DIVIDER TX/RX D313,D314 HSB88AS-E POWER...

  • Page 42: Level Diagram

    TM-281A LEVEL DIAGRAM Receiver Section Center Frequency 49.95MHz 450kHz W : –80.5dBm N : –78.0dBm W : –123.5dBm W : –120.0dBm W : –103.5dBm W : –107.5dBm W : –109.0dBm CF501 W : –97.0dBm /CF502 N : –123.5dBm N : –120.0dBm N : –104.0dBm...
  • Page 43 TM-281A LEVEL DIAGRAM 450kHz Audio Frequency W : –84.5dBm N : –84.5dBm CF501 /CF502 0.54Vrms 0.45Vrms 0.42Vrms 0.45Vrms 0.47Vrms 10mVrms 0.70Vrms 0.64Vrms IC501 IC709 IC709 IC709 IC709 IC705 IC715 Q706 vel meter. 12dB SINAD.) To make measurements in the AF section, connect the AC level meter.

  • Page 44: Specifications

    Bp 58416 Villepinte, 95944 Roissy Ch De Gaulle Cedex Suite 2504, 25/F, Tower 2, Nina Tower, No. 8 Yeung Uk Road, Tsuen Wan, New Territories, Hong Kong KENWOOD House, Dwight Road, Watford, Herts., WD18 9EB United Kingdom 1 Ang Mo Kio Street 63, Singapore 569110...
  • Page 45 TM-281A TM-281A PC BOARD PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 A/2) Component side view (J79-0316-09 A/2) Ref.
  • Page 46 TM-281A TM-281A PC BOARD PC BOARD TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION TX-RX UNIT (X57-8130-XX) (A/2): TX-RX SECTION -10: K -21: M2 -22: M3 -23: M4 -10: K -21: M2 -22: M3 -23: M4 Foil side view (J79-0316-09 A/2) Foil side view (J79-0316-09 A/2) Ref.
  • Page 47 TM-281A TM-281A PC BOARD PC BOARD TX-RX UNIT (X57-8130-XX) (B/2): DISPLAY SECTION TX-RX UNIT (X57-8130-XX) (B/2): DISPLAY SECTION -10: K -21: M2 -22: M3 -23: M4 -10: K -21: M2 -22: M3 -23: M4 Component side view (J79-0316-09 B/2) Component side view (J79-0316-09 B/2) J79-0316-09 B/2 Ref.
  • Page 48 TX-RX UNIT (X57-8130-XX)(A/2) : TX-RX SECTION TX-RX UNIT (X57-8130-XX)(B/2) : DISPLAY SECTION IC302 RA60H1317M231 R:5.00V INT SP X57-8130-XX R766 R767 R768 POWER MODULE RX VCO Q1,2 D3,5 R:0.73V SWITCHING BUFFER AMP D9,10 SPOUT OSCILLATOR T:0.72V R:6.03V R:4.82V FREQENCY 4.5p RF AMP T:4.76V RF SWITCH T:5.55V...
  • Page 49 TX-RX UNIT (X57-8130-XX B/2): Display section TX-RX UNIT (X57-8130-XX A/2): TX-RX section 2SC4649(N,P) MB15A02PFV2E1 RX: 136.000~173.9975MHz (K,M2,M3) PLLE D306,D307 144.000~147.9975MHz (M4) PLL IC L407CDB TX: 136.000~173.9975MHz (M2,M3) Q303 IC302 D9,D10 D309,D311 144.000~147.9975MHz (K,M4) RD00HVS1-T113 RA60H1317M231 2SC5108(Y)F UPB1509GV 2SC5108(Y)F HSC277 JDP2S12CR MCH3914(7)-H 16.8MHz POWER...
  • Page 50 Receiver Section Center Frequency 49.95MHz 450kHz Audio Frequency W : –80.5dBm W : –84.5dBm N : –78.0dBm N : –84.5dBm W : –123.5dBm W : –120.0dBm W : –103.5dBm W : –107.5dBm W : –109.0dBm W : –97.0dBm CF501 N : –123.5dBm N : –120.0dBm N : –104.0dBm N : –108.5dBm...

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