Kenwood TH-K20A Service Manual Download Page 1

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144MHz FM TRANSCEIVER

TH-K20A/K20E

SERVICE MANUAL

This product uses Lead Free solder

his product complies with the

RoHS

directive for the European market.

CONTENTS

DISASSEMBLY FOR REPAIR .....................2

CLONE MODE .............................................3

CIRCUIT DESCRIPTION .............................4

SEMICONDUCTOR DATA ...........................7

COMPONENTS DESCRIPTION ..................9

PARTS LIST ...............................................10

EXPLODED VIEW ......................................16

PACKING ...................................................17

ADJUSTMENT ...........................................18

PC BOARD

TX-RX UNIT (X57-821X-XX) ...................22

SCHEMATIC DIAGRAM ............................26

BLOCK DIAGRAM .....................................30

LEVEL DIAGRAM ......................................32

OPTIONAL ACCESSORIES

BT-16 (Battery Case) .............................33

EMC-11

(Clip Microphone with Earphone) ..33

PB-46L (Li-ion Battery Pack) ................33

KVC-22

(DC Vehicular Chager Adapter) ..33

SPECIFICATIONS ......................................35

Helical antenna
M: (T90-1018-35)
K,E: (T90-1044-15)

Plastic cabinet assy
(A02-4158-03)

Knob (Volume)
(K29-9503-03)

Knob(Encoder)
(K29-9504-03)

Key top (16 keys)
(K29-9502-02)

When performing the TH-K20 adjustment, a personal
computer, programming interface and tuning software are
required.

Summary of Contents for TH-K20A

Page 1: ...0 EXPLODED VIEW 16 PACKING 17 ADJUSTMENT 18 PC BOARD TX RX UNIT X57 821X XX 22 SCHEMATIC DIAGRAM 26 BLOCK DIAGRAM 30 LEVEL DIAGRAM 32 OPTIONAL ACCESSORIES BT 16 Battery Case 33 EMC 11 Clip Microphone with Earphone 33 PB 46L Li ion Battery Pack 33 KVC 22 DC Vehicular Chager Adapter 33 SPECIFICATIONS 35 Helical antenna M T90 1018 35 K E T90 1044 15 Plastic cabinet assy A02 4158 03 Knob Volume K29 95...

Page 2: ...tion reserves the right to make changes to any products herein at any time for improvement purposes DISASSEMBLY FOR REPAIR 1 Separating the Case Assembly from the Chassis 1 Remove the two knobs a 2 Remove the two screws b 3 Pull off the cap from SP MIC jack c 4 Expand the right and left sides of the bottom of the case assembly Iift the chassis and remove it from the case assembly d 5 Taking care n...

Page 3: ...ode CLONE appears on the display 4 Turn the target transceiver power ON 5 Press the CALL key on the source transceiver while SEND is displayed The data of the source is sent to the target While the target is receiving data RECV appears on the display When cloning is completed the END appears on the source and target display 6 Turn the source and target transceiver power OFF Note The Model name and...

Page 4: ...MCF to cut the adjacent spurious and provide the optimum charac teristics such as adjacent frequency selectivity RX 136 173 995MHz K E M 174 85 212 845MHz 1st MIX MCF SP MIC CF 450kHz ANT ANT SW RF AMP IF SYSTEM X2 doubler PLL VCO 38 85MHz 38 4MHz TX AMP T R SW AF AMP MIC AMP AF filter TCXO 19 2MHz RF AMP TX 136 173 995MHz M 144 147 995MHz K 144 145 995MHz E 1st Lo TX 136 173 995MHz M 144 147 995M...

Page 5: ...ier circuit 2 3 IF Amplifier Circuit The first IF signal is passed through a four pole mono lithic crystal filter XF200 to remove the adjacent channel signal The filtered first IF signal is amplified by the first IF ampli fier Q202 and then applied to the lF system IC IC200 The IF system IC provides a second mixer second local oscillator limiting amplifier quadrature detector and RSSI Received Sig...

Page 6: ...equency tuning and modulation of the TCXO are done to apply a voltage to pin 1 of the TCXO The output of the TCXO is applied to pin 1 of the PLL IC The VCO consists of 1VCO and covers a dual range of the 144 00 174 00MHz and the 182 85 212 85MHz The VCO generates 182 85 212 85MHz for providing to the first local signal in receive The PLL IC consists of a prescaler reference divider phase comparato...

Page 7: ...PIN I Data input from EEPROM 31 34 COM0 COM3 O LCD common output H Active 35 66 SEG0 SEG31 O LCD segment output H Active 67 LEDR O TX LED Red control H Lights 68 LEDG O BUSY LED Green control H Lights 69 5VC O 5V MIC AMP power switch control L Active 70 5MSC O 5MS main power switch control L Active 71 SPM O Speaker mute control L Mute Pin No Port Name I O Function 72 MONI I MONI key switch input L...

Page 8: ...e adjust 12 Vout6 O TCXO frequency adjust 13 Vin6 I Connect to ground 14 VDAREF1 Reference voltage 1 for DAC 1 8V 15 VDAREF2 Reference voltage 1 for DAC 5 0V 16 RESET I Reset 17 GND Ground 18 Vin7 I Connect to ground 19 Vout7 O RX BPF tuning adjust 20 Vout8 O TX power adjust 21 Vin8 I Connect to ground 22 Vin1 I From MIC output 23 Vout1 O MIC level contorol and mute 24 Vout2 O RX AF mute control P...

Page 9: ...tive ON SM H Q302 SP mute control switch for pop noise Active ON Q303 Speaker mute switch for AF signal line Active ON Ref No Use Function Operation Condition Compatibility Q304 Power supply 5MS switch Active ON 5MSC L Q305 Speaker mute switch for AF signal line Active ON Q306 IC power supply switch for AF power IC Active ON Q307 Power supply 5R switch Active ON 5RC L Q308 Power supply 5T switch A...

Page 10: ...lor Black Red Orange Yellow Green Blue Violet ppm C 0 80 150 220 330 470 750 Code C D G J K M X Z P No code 0 25 0 5 2 5 10 20 40 80 100 More than 10µF 10 50 20 20 0 Less than 4 7µF 10 75 2nd word A B C D E F G H J K V 1st word 0 1 0 1 25 1 6 2 0 2 5 3 15 4 0 5 0 6 3 8 0 1 10 12 5 16 20 25 31 5 40 50 63 80 35 2 100 125 160 200 250 315 400 500 630 800 3 1000 1250 1600 2000 2500 2150 4000 5000 6300 ...

Page 11: ...X57 54 1B T07 0787 05 SPEAKER 56 2C T90 1018 35 HELICAL ANTENNA ACCESSORY M 57 2C T90 1044 15 HELICAL ANTENNA ACCESSORY K E 58 1C W08 1246 15 AC ADAPTER ACCESSORY M E 59 1C W08 1247 15 AC ADAPTER ACCESSORY K 61 2D W08 1249 35 CHARGER ACCESSORY 62 1C W09 1073 25 BATTERY ASSY ACCESSORY X57 8210 12 TX RX UNIT FOR SERVICE K X57 8210 21 TX RX UNIT FOR SERVICE M X57 8212 72 TX RX UNIT FOR SERVICE E 101 ...

Page 12: ...103K CHIP C 0 010UF K C229 CC73HCH1H050C CHIP C 5 0PF C C230 CC73HCH1H100B CHIP C 10PF B C231 CC73HCH1H050C CHIP C 5 0PF C C232 CC73HCH1H101J CHIP C 100PF J C233 CK73HB1H102K CHIP C 1000PF K C234 CK73HB1E103K CHIP C 0 010UF K C235 CK73HB1H102K CHIP C 1000PF K C237 CC73HCH1H220J CHIP C 22PF J C239 240 CK73HB1H102K CHIP C 1000PF K C244 CK73HB1H102K CHIP C 1000PF K C245 CC73HCH1H020B CHIP C 2 0PF B C...

Page 13: ...TOR 10UH L9 L40 1285 71 SMALL FIXED INDUCTOR 120NH L10 L40 2775 71 SMALL FIXED INDUCTOR 27NH L11 L40 8275 71 SMALL FIXED INDUCTOR 82NH L13 L40 4763 92 SMALL FIXED INDUCTOR 4 7NH L101 L40 6875 71 SMALL FIXED INDUCTOR 68NH L103 L40 1085 71 SMALL FIXED INDUCTOR 100NH L104 L40 3375 71 SMALL FIXED INDUCTOR 33NH L105 L41 8275 53 SMALL FIXED INDUCTOR 82NH L106 L34 4577 05 AIR CORE COIL 9T L107 L34 4574 0...

Page 14: ...CHIP R 100K J 1 16W R239 RK73HB1J394J CHIP R 390K J 1 16W R240 RK73HB1J104J CHIP R 100K J 1 16W R241 RK73HB1J184J CHIP R 180K J 1 16W R243 RK73HB1J105J CHIP R 1 0M J 1 16W R246 RK73HB1J104J CHIP R 100K J 1 16W R247 RK73HB1J332J CHIP R 3 3K J 1 16W R248 RK73HB1J152J CHIP R 1 5K J 1 16W R249 RK73HB1J102J CHIP R 1 0K J 1 16W R251 RK73HB1J105J CHIP R 1 0M J 1 16W R252 253 RK73HB1J472J CHIP R 4 7K J 1 ...

Page 15: ...R466 RK73GB2A000J CHIP R 0 J 1 10W R470 RK73HB1J473J CHIP R 47K J 1 16W S417 S70 0514 05 TACT SWITCH MONI S418 2B S70 0414 05 TACT SWITCH PTT MIC300 2A T91 0673 05 MIC ELEMENT D1 2 1SV325F VARIABLE CAPACITANCE DIODE D3 HSC277 DIODE D4 5 HVC350B VARIABLE CAPACITANCE DIODE D6 DA2S101 DIODE D7 8 HSC277 DIODE D9 11 DA2S101 DIODE D101 102 HVC131 DIODE D103 105 RN142S DIODE D200 201 HVC350B VARIABLE CAP...

Page 16: ...view of the PCB that part does not come with the PCB These parts must be ordered separately A A B B Cx13 M K E 48 49 51 52 54 33 23 1 47 TX RX unit 32 46 26 3 29 36 19 7 VR300 S419 7 700 701 J300 J301 2 A N09 2438 05 B N80 2606 43 C N83 2005 48 107 MIC300 21 24 27 34 4 8 31 106 105 103 101 102 104 X57 X57 X57 X57 X57 X57 X57 700 700 702 S418 X57 6 3 2 1 B A ...

Page 17: ...IXTURE 41 ITEM CARTON CASE 59 AC ADAPTER 58 AC ADAPTER 57 HELICAL ANTENNA 56 HELICAL ANTENNA T90 1018 35 M W08 1247 15 K T90 1044 15 K E 42 Belt clip J29 0756 05 62 BATTERY ASSY W09 1073 25 B62 2371 00 E B62 2372 00 E B62 2373 00 E B62 2374 00 E 38 PACKING FIXTURE H12 4326 02 K W08 1249 35 H12 4324 02 K 13 16 INSTRUCTION MANUAL H52 2486 02 K W08 1246 15 M E B62 2375 00 M 18 INSTRUCTION MANUAL K TH...

Page 18: ... and the current is 3A or more 2 The standard voltage is 7 5V Power supply voltage range 6V 9V 2 DC Ammeter DC A 1 Class 1 ammeter 17 ranges and other features 2 The full scale can be switched between 300mA and 3A 3 A cable with low internal loss must be used 3 Frequency Counter f counter 1 Frequencies of up to 1GHz or so can be measured 2 The sensitivity can be changed to 250MHz or below and meas...

Page 19: ...ations for Tuning the Transceiver Before attempting to tune the transceiver connect the unit to a suitable power supply Whenever the transmitter is tuned the unit must be con nected to a suitable dummy load i e power meter The speaker output connector must be terminated with a 8 dummy load and connected to an AC voltmeter and an audio distortion meter or a SINAD measurement meter at all times duri...

Page 20: ...ipment Unit Terminal Unit Parts Method 1 Frequency 1 Tuning point High Press Transmit button f counter TX RX ANT MCP 5T 173 900MHz 50Hz 2 High Transmit Power and Protective Current 1 Tuning point Low Center High 3 points BATT terminal voltage 7 5V Press Transmit button Power meter Ammeter MCP 5T 5 5W 0 1W 2 0A or less 3 Low Transmit Power 1 Tuning point Low Center High 3 points BATT terminal volta...

Page 21: ...s Filter 1 Tuning point Low Center High 3 points SSG output 90dBm 7 08µV SSG DEV 3 0kHz SSG DVM Oscilloscope AF VM TX RX ANT SP MIC connector MCP 5T Automatic Adjust ment Press Start button of Auto Tuning Press Apply button to store the adjust ment value after the automatic adjust ment has finished 2 Sensitivity Check Narrow 1 Tuning point Low High 2 points SSG output 120dBm 0 22µV SSG DEV 1 5kHz ...

Page 22: ...E PC BOARD Ref No Address IC301 8Q IC304 6P IC305 6M IC306 5N IC307 4P IC308 4N IC401 6J Q300 6Q Q301 5P Ref No Address Q302 5P Q303 4O Q304 7N Q305 4O Q306 5P Q308 4N Q400 7H D300 8O D301 5M D302 5N Ref No Address D304 5N D305 9O D404 5C D405 5D D406 5E D407 5F D408 5D D409 5E TX RX UNIT X57 821X XX 0 11 K 0 20 M 2 71 E Ref No Address Ref No Address D410 5E D411 5E D415 2J D416 4G D417 8G D418 3F...

Page 23: ... R351 R353 R354 R355 R357 R358 R359 C321 C322 R360 R362 R363 R364 R365 C329 R366 R367 R368 C332 C333 R370 C334 C335 C336 R372 C337 C338 R374 C339 R376 R377 R378 R379 C340 C341 C342 R380 C344 R389 C351 C352 C353 C354 C356 C358 C359 D300 C360 D301 D302 C363 D304 C364 D305 C365 C366 C367 C369 C371 C372 C373 C375 C376 C377 C379 IC300 C380 IC301 C381 C383 IC304 IC305 IC306 IC307 IC308 CP1 50 51 1 3 4 5...

Page 24: ...7 C154 R385 R386 C157 R387 R388 C160 D101 D102 D103 C357 D104 Q204 C361 Q401 Q402 Q403 Q404 L211 L213 L214 IC302 IC303 C386 R326 S418 PTT MONI VR300 S419 J301 J300 1 4 5 8 1 4 5 8 1 4 5 8 G D S G D105 TH K20A K20E PC BOARD Ref No Address IC1 8Q IC200 8M Ref No Address Q7 9Q Q101 4N Q102 3N Q200 8M Q201 9O Q202 8N Q203 6M Q204 6J Ref No Address Q401 9J Q402 8J D1 5P D2 5P D3 6P D4 5Q D5 5Q D6 5P D7...

Page 25: ...70 L104 C271 L105 C272 L106 C273 L113 IC200 R101 R102 R103 R104 R105 R107 R108 D10 D11 R109 CF200 R111 R112 R113 R114 R115 R116 R120 L1 R121 L2 L3 R124 L4 L5 R125 L6 R127 L8 L9 R129 R324 R130 L10 L11 L13 C101 R331 C102 R332 R333 C104 R334 C105 TH101 C106 C107 C108 C109 C110 IC1 C112 C113 C115 R10 R11 R12 R14 R15 C125 C127 R18 R19 C323 R20 R21 R22 R23 R24 Q1 R25 Q2 R26 Q3 R27 Q4 R28 Q5 Q6 Q7 C330 C...

Page 26: ... SEG25 SEG26 SEG27 SEG28 SEG29 SEG30 SEG31 S419 C B A CN300 1 2 D423 D422 D425 R450 1 2k R451 1 2k D424 R453 100k R452 100k R464 27k R376 0 C359 0 01u S412 D409 D405 1SS388F S409 D406 1SS388F S406 S415 D411 DA2S101 S413 S411 S407 S410 S408 D410 DA2S101 S405 D404 1SS388F S414 D408 D407 1SS388F S416 R466 Q307 LTA023JEBFS8 C361 0 22u C360 0 22u C379 220p R378 27k C381 0 1u IC305 XC6120N302N G 1 NC 2 ...

Page 27: ...99 100 R400 220k R403 220k R401 220k C404 C405 C406 C407 R402 R465 4 7 k CP1 C386 0 047u IC400 EX25064ATA00A 1 S 2 Q 3 W 4 VSS 5 D 6 C 7 HoLD 8 VCC EEPROM 5M SB 5T 5C 5R SB B DAT CLK RESET 5M GND MODE CLK DAT E2PCS KEYIT KEYIS HSDO LSDO WKUPO VREF MODE XCIN XCOUT RESET XOUT VSS XIN VCC BSFT INPTT 5RC ENC2 ENC1 RxD TxD PLLEN PLLPS PLLLD NC 5TC 5CC COM0 COM1 COM2 COM3 SEG0 SEG1 SEG2 SEG3 SEG4 SEG5 S...

Page 28: ... R5 1k R2 2 7k D3 HSC277 R6 100k R8 10k R7 100k R9 100k C9 1u C10 8 p L6 10u C12 1u 6 3 D5 HVC350B C15 10p C1 7 9 p MCH3914 7 H Q3 C19 0 01u R10 22 C2 0 1000p 2SC5108 Y F Q4 C22 0 5p C18 R11 4 7k D6 DA2S101 C16 22u 10 C13 1000p 2SC5383 T111 Q2 R14 1k C23 1000p L1 220n C6 0 022u L4 2 7 n C1 0 18u R388 1k R386 82k R385 1k R322 3 3k L2 180n R1 2 220 L8 C37 0 15u C4 0 022u C8 1000p C11 1000p R18 0 Q1 ...

Page 29: ... C249 3 9p C254 1000p R229 R228 1k L209 C261 39p C265 47p C246 3 9p C235 C248 1p C259 1000p C247 1000p D201 HVC350B D200 HVC350B C256 47p R240 C245 2p C244 1000p R230 D203 HVC350B 3SK318 Q203 R239 3SK318 Q204 C255 C250 2p R243 1M C253 R236 82 R235 47 L201 560n L200 560n KTC4080E P Q201 KTC4080E P Q202 L202 820n R225 4 7 C234 0 01u C240 1000p R119 0 F101 R215 0 R208 18 k R210 68k CF200 R207 2 7k C2...

Page 30: ...PF LTC014EEBFS8 D1 D2 1SV325F D4 HVC350B MOD CONV D A D5 HVC350B ASSIST 144 000 145 995MHz E IC300 5 8 R2A20178NP IC300 6 8 R2A20178NP Q6 INVERT LTC014EEBFS8 PLLD 5MS FREQ 5MS B30 1782 05 Q403 D426 GRN LEDG LTC014EEBFS8 LTC014EEBFS8 5MS DCSW B30 1779 05 Q404 D427 RED LEDR 3 3V REG Q7 2SC5383 T111 DCSW DCSW DCSW SB DATA PROTECT SB D301 GN1G BATT 7 5V VOLIN B VR300 R31 0684 05 PROTECT D302 RB521S 30...

Page 31: ...D7 D8 AMP RSSI V REF L71 0669 05 L72 1042 05 5T B 5VC DC SW Q200 TH101 DA2S101 D6 5C KTC4080E P SQL LTA023JEBFS8 IC301 NJM12904RB1 LIMITER MIC AMP 5C CONV D A FILTER AF IC303 NJM12904RB1 LSDI WID NAR 2nd Local Q5 2SC5636 RF AMP RD07MUS2BT112 Q103 AMP CD CD200 L79 1474 05 S8 5C MIC INT SP MUTE SW SB Q303 MUTE SW Q305 LTC044EEBFS8 F301 Q302 SPM Q301 INT 2SK3577 A DC SW DC SW LTC044EEBFS8 0 315A VOLO...

Page 32: ...F coupling capacitor Receiver Section Transmitter Section FM IF SYSTEM DAC SSG 53dBm ANT 56 1dBm 74 2dBm 66 8dBm 50 8dBm 52 8dBm 40 3dBm 57 1dBm 29 1dBm 31mVrms 27mVrms 2 4Vrms 2 3Vrms 2 0Vrms C265 C256 C248 C273 C228 C223 C217 C322 C381 C357 SP 500mW Q303 Q305 IC307 IC300 IC200 Q202 XF200 MIXER Q203 Q204 RF CENTER FREQUENCY IF1 38 85MHz IF2 450kHz AF 1kHz IC300 DAC AF AMP C22 29 1dBm VCO C27 C34 ...

Page 33: ... EMC 11 Clip Microphone with Earphone KVC 22 DC Vehicular Chager Adapter KNB 65L Li ion Battery Pack Specifications Earphone unit Impedance 72 15 16 15 Speaker only Nominal input power 20mW Microphone unit Impedance 1 5k 30 Sensitivity 42dB 3dB at 1000Hz Specifications Voltage 7 4V Battery capacity typ 1520mAh min 1460mAh ...

Page 34: ...TH K20A K20E 34 MEMO ...

Page 35: ...itter RF output power with KNB 63L KNB 65L High 5 5W Medium 2W Low 1W Modulation Reactance Maximum frequency deviation Within 5kHz Spurious emission Less than 60dB Modulation distortion Less than 5 300Hz 3kHz Microphone impedance 2k Receiver Circuit type Double super heterodyne Intermediate Frequency IF 1st IF 38 85MHz 2nd IF 450kHz Sensitivity 12dB SINAD Less than 0 16µV Squelch sensitivity Less ...

Page 36: ...TH K20A K20E ...

Page 37: ...C342 R380 C344 R389 C351 C352 C353 C354 C356 C358 C359 D300 C360 D301 D302 C363 D304 C364 Q400 D305 C365 C366 C367 C369 C371 C372 C373 C375 C376 C377 C379 IC300 C380 IC301 C381 C383 IC304 IC305 IC306 IC307 IC308 CV CP1 1 25 26 50 51 75 76 100 1 3 4 5 1 6 7 12 13 18 19 24 1 4 5 8 1 4 5 8 1 10 5 6 1 2 SPG SPK 1 2 4 3 1 5 4 3 J79 0325 09 MODE GND RESET 5M MIC300 B GND 5R B C374 TH K20A K20E PC BOARD ...

Page 38: ...0 IC1 C112 C113 C115 R10 R11 R12 C316 C317 R14 C318 R15 C319 C125 C127 R18 R19 C129 C320 C323 R20 C324 R361 C325 R21 C326 R22 C327 R23 C133 C134 C328 R24 Q1 R25 C135 Q2 C136 R26 Q3 C137 R27 Q4 C138 R28 R369 Q5 C139 Q6 Q7 C330 C331 C140 R30 C141 R31 R32 R33 C144 R34 C146 R2 R36 C147 R37 R3 C148 R4 R38 R5 R39 R6 R7 R8 R9 C150 R40 R41 C345 C151 R382 C152 C347 R383 R43 C153 C154 R385 C155 R45 C156 R46...

Page 39: ...401 220k CF200 C321 0 18u C404 C405 C406 C407 R207 2 7k CN300 1 2 R387 33k C319 0 18u D423 D422 D425 R450 1 2k R451 1 2k D424 C266 3p R246 100k R226 0 R247 3 3k C239 R227 330 C237 22p R232 0 C251 1000p R248 1 5k C127 C125 C133 L114 5T L113 3T C5 R3 1k R4 15k C2 0 033u C3 1u C 7 0 5p D4 HVC350B R5 1k R2 2 7k D3 HSC277 R6 100k R 8 10k R7 100k R9 100k C9 1u C 1 0 8p L6 10u C 1 2 1u 6 3 D5 HVC350B C 1...

Page 40: ... PLLE DAT CLK ENC2 ENC1 5MSC 5RC 5TC 5CC PLLD LSDI 5M 2nd Local 19 2MHz Q5 2SC5636 RF AMP RD07MUS2BT112 Q103 AMP SHIFT LPF CD CD200 L79 1474 05 LTC014EEBFS8 5C MIC INT SP MUTE SW SB Q303 MUTE SW Q305 LTC044EEBFS8 F301 Q302 SPM Q301 INT 2SK3577 A DC SW DC SW D1 D2 1SV325F D4 HVC350B MOD CONV D A D5 HVC350B ASSIST 144 000 145 995MHz E LTC044EEBFS8 0 315A VOLOUT MIC SPG TXD SPK AFO PTT RXD MIC IM 5MS...

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