LG LH-T6740 Service Manual Download Page 8

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ELECTRICAL TROUBLESHOOTING GUIDE

INSERT

POWER CORD.

TURN ON

THE RED LED?

IS POWER ON?

CHECK POWER PLUG

AND POWER SUPPLY CIRCUIT.

DOES INITIAL

READ WORK?

DOES IT PLAY?

YES

CHECK POWER SUPPLY CIRCUIT.

CHECK LASER CIRCUIT.

CHECK TRACKING SERVO CIRCUIT.

TURN POWER ON.

CHECK FOCUS CIRCUIT.

CHECK DISC.

DOES IT OUTPUT

AUDIO?

YES

CHECK AUDIO CIRCUIT.

1. Power check flow

SECTION 2. AUDIO PART

Summary of Contents for LH-T6740

Page 1: ...DVD CD RECEIVER SERVICE MANUAL P N 3829RDT050K NOVEMBER 2005 MODEL LH T6740 LH T6740A LHS T6740C LHS T6740T LHS T6740W SERVICE MANUAL MODEL LH T6740 LH T6740A LHS T6740C LHS T6740T LHS T6740W CD R RW ...

Page 2: ... BLOCK DIAGRAM 2 5 SCHEMATIC DIAGRAMS 2 7 WIRNG DIAGRAMS 2 21 PRINTED CIRCUIT DIARGAMS 2 23 SECTION 3 DVD PART DVD PART ELECTRICAL TROUBLESHOOTING GUIDE 3 1 DETAILS AND WAVEFORMS ON SYSTEM TEST AND DEBUGGING 3 8 BLOCK DIAGRAM 3 21 DVD PART SCHEMATIC DIAGRAMS 3 25 SECTION 4 EXPLODED VIEWS 4 1 SECTION 5 SPEAKER PART 5 1 SECTION 6 REPLACEMENT PARTS LIST 6 1 ...

Page 3: ...ver be touched 4 Laser beams may damage the eyes Absolutely never permit laser beams to enter the eyes Also NEVER switch ON the power to the laser output part lens etc of the pick up if it is damaged 5 Cleaning the lens surface If there is dust on the lens surface the dust should be cleaned away by using an air bush such as used for camera lens The lens is held by a delicate spring When cleaning t...

Page 4: ... replacing a component part first disconnect the power supply lead wire from the unit 2 All equipment measuring instruments and tools must be grounded 3 The workbench should be covered with a conductive sheet and grounded When removing the laser pick up from its conductive bag do not place the pick up on the bag This is because there is the possibility of damage by static electricity 4 To prevent ...

Page 5: ...harges sufficient to damage ESD devices 5 Do not use freon propelled chemicals These can generate electrical charges sufficient to damage ESD devices 6 Do not remove a replacement ESD device from its protective package until immediately before you are ready to install it Most replacement ESD devices are packaged with leads electrically shorted together by conductive foam aluminum foil or comparabl...

Page 6: ... 1 5 SPECIFICATIONS ...

Page 7: ... 1 6 MEMO ...

Page 8: ...UG AND POWER SUPPLY CIRCUIT DOES INITIAL READ WORK DOES IT PLAY YES NO YES YES OK NO YES NO NO CHECK POWER SUPPLY CIRCUIT CHECK LASER CIRCUIT CHECK TRACKING SERVO CIRCUIT TURN POWER ON CHECK FOCUS CIRCUIT CHECK DISC DOES IT OUTPUT AUDIO YES NO CHECK AUDIO CIRCUIT 1 Power check flow SECTION 2 AUDIO PART ...

Page 9: ...High Check if IC101 PIN11 is High Check if IC101 PIN 17 46 72 90 is high 5V Check if IC101 PIN26 is High Replace IC101 Does CD DVD appear at FLD Reconnet it Refer to SMPS OK Refer to oscillator Circuit Check DVD Reset Waveform Check IC101 Reset Wavefrom Check 5V line Check Power dection Circuit Does LOADING appear at FLD Does no Disc or Time appear at FLD Check if DVD an Audio Micom Interface is O...

Page 10: ... 2 3 3 FRONT CIRCUIT 1 2 ...

Page 11: ... 2 4 4 FRONT CIRCUIT 2 2 ...

Page 12: ... BLOCK DIAGRAM 2 5 2 6 ...

Page 13: ...2 7 2 8 SCHEMATIC DIAGRAMS FRONT SCHEMATIC DIAGRAM ...

Page 14: ...2 9 2 10 MICOM SCHEMATIC DIAGRAM ...

Page 15: ...2 11 2 12 I O SCHEMATIC DIAGRAM ...

Page 16: ...2 13 2 14 DSP SCHEMATIC DIAGRAM ...

Page 17: ...2 15 2 16 AMP SCHEMATIC DIAGRAM ...

Page 18: ...2 17 2 18 SMPS WIDE SCHEMATIC DIAGRAM ...

Page 19: ...2 19 2 20 POWER SCHEMATIC DIAGRAM ...

Page 20: ...2 21 2 22 WIRING DIAGRAMS ...

Page 21: ...2 23 2 24 PRINTED CIRCUIT DIAGRAMS MAIN P C BOARD COMPONENT SIDE ...

Page 22: ...2 25 2 26 MAIN P C BOARD SOLDER SIDE ...

Page 23: ...2 27 2 28 FRONT P C BOARD SOLDER SIDE FRONT P C BOARD COMPONENT SIDE ...

Page 24: ...2 29 2 30 POWER P C BOARD ...

Page 25: ...2 31 2 32 MEMO MEMO ...

Page 26: ... 3 1 1 Power check flow ELECTRICAL TROUBLESHOOTING GUIDE SECTION 3 DVD PART ...

Page 27: ...ay Close to Closed position NO SLED at Inner Side SLED Moves to Inner Positi on NO YES YES Reci eve OPEN CLOSE Key 1 Execute Pressed Key IR Key 2 System operation Routine Loop NO 1 Stop Playback Open Tray 2 Display tray open message LOGO Receive CLOSE Key NO YES YES 1 Judge whether have disc and disc type 2 Jump to related disc reading procedure ...

Page 28: ... PCBA NO Make sure the main PCBA don t short on VCCs and switch it on YES Is 3 3V and 1 8V DC outputs normal on main PCBA Check the regulators or related diodes NO YES Connect to PC RS232 Cable and update the FLASH memory code Update FLASH successfully A YES NO 1 Check 27MHz system clock 2 Check system reset circuit 3 Check FLASH R W enable signal PRD RWR 4 Check RS232 SIGNALS 5 Check FLASH Memory...

Page 29: ... damaged MT1389 VIDEO outputs properly Check the related circuit of MT1389 Have TV signal output Check the filtering and amp circuit of TV signal Check AV cable connection to TV set Does Tray move inside when it is not at closed position Normal TROUT TRIN signals Check the load OPEN CLOSE switch Normal TRCLOSE TROPEN signal Normal LOAD LOADsignal Check the cable connection between main PCBA and lo...

Page 30: ...r than 1 4V Check the related circuit of FMSO SL and SL output properly Check the amp circuit on motor driver Check the cable connection with MECHA Do not put in disc and tray close C Optical Lens has movements for searching Focus Proper FOSO outputs to motor driver Check FOSO connection on MT1389 and motor dirver Proper F F outputs Check the amp circuit on motor dirver Check cable connect on with...

Page 31: ...Laser turns on when reading disc NO NO YES NO YES YES NO LD01 or LD02 output properly Check the laser power circuit on MT1336 and connecting to power transistor Collector voltage of power transistor is OK Check the related circuit on laser power transistor Check cable connection between transistor ouput and pick up head Put disc in Laser off Disc ID is correct Proper RFL signal on MT1389 Check the...

Page 32: ... on MT1389 and motor dirver Check the tracking control amp circuit on motor driver Check cable connection on pick up head Disc is play Check RFO RFLVL signal waveform NO NO YES YES YES Focus ON OK Proper signals on A B C D of MT1389 Check connections between MT1389 and pick up head Check FEO signal on MT1389 Check FOSO signal on MT1389 Check the FOSO connection on MT1389 and motor driver YES NO ...

Page 33: ...ines on MT1389 NO YES Check the cable connection on Front pannel TEST END YES Normal Audio output when disc playback Audio PWM IC received correct data stream Check connection between MT1379 Audio PWM IC Normal Audio PWM IC out Check the related circuit of Audio PWM IC Check Audio filter amplify mute circuit NO NO NO YES YES YES E NO ...

Page 34: ... 3 9 FIG 1 1 FIG 1 2 DETAILS AND WAVEFORMS ON SYSTEM TEST AND DEBUGGING 1 SYSTEM 27MHz CLOCK RESET FLASH R W SIGNAL 1 MT1379 main clock is at 27MHz X501 2 MT1336 reset is high active ...

Page 35: ... 3 10 FIG 1 3 FIG 1 4 3 RS232 waveform during procedure Downloading 4 Flash R W enable signal during download Downloading ...

Page 36: ... 3 11 FIG 2 1 FIG 3 1 2 SDRAM CLOCK 1 MT1379 main clock is at 27MHz X501 3 TRAY OPEN CLOSE SIGNAL ...

Page 37: ... 3 12 FIG 4 1 FIG 5 1 4 SLED CONTROL RELATED SIGNAL NO DISC CONDITION 5 LENS CONTROL RELATED SIGNAL NO DISC CONDITION ...

Page 38: ... 3 13 FIG 6 1 FIG 7 1 6 LASER POWER CONTROL RELATED SIGNAL NO DISC CONDITION 7 DISC TYPE JUDGEMENT W VEFORM ...

Page 39: ... 3 14 FIG 7 2 DVD FIG 7 3 CD ...

Page 40: ... 3 15 FIG 7 4 CD FIG 8 1 DVD 8 FOCUS ON W VEFORM ...

Page 41: ... 3 16 FIG 8 2 CD FIG 9 1 9 SPINDLE CONTROL W VEFORM NO DISC CONDITION ...

Page 42: ... 3 17 10 TRACKING CONTROL RELATED SIGNAL System checking FIG 10 1 DVD FIG 10 2 CD ...

Page 43: ... 3 18 FIG 11 1 DVD FIG 12 1 11 MT1389 AUDIO OPTICAL AND COAXIAL INPUT SPDIF 12 MT1389 VIDEO OUTPUT WAVEFORM 1 100 ...

Page 44: ... 3 19 ADAT0 3 FIG 12 2 FIG 13 1 2 COMPOSITE VIDEO SIGNAL 13 MT1389 AUDIO OUTPUT TO PWM IC ...

Page 45: ... 3 20 FIG 14 1 14 AUDIO OUTPUT FROM PWM IC ...

Page 46: ...D FEEDING MOTOR SLED M VD33D VD33D VD18 VD33 3V3M IC605 MM1623XFBE VIDEO BUFFER RS232_TXD IECDAOUT COAXIAL SPDIF D2_T 1 3 SCART_16 9 RGB_SEL 3V3M CDLD DVDLD SVREF21 5V 8V HOMESW INSW OUTSW ROMDATA 0 7 5 2VA IC101 AUDIO MICOM M_REQ POWER BOARD VFD_RXD S_REQ 5 2VA 8V DMUTE IIC VFD DAC_SCK IC603 4M 16BIT 4Bank SDRAM VD33D MA 00 11 DMCLK CSJ BA0 BA1 DQM WEJ CASJ RASJ IIC VFD DAC_TXD IC601 MTK MT1389 1...

Page 47: ...SO DMSO TROPEN ADIN F F T T SL SL LOAD LOAD LD0 1 LDO 2 IOA MDI 1 ALPC V20 PICKSEL LIMIT TRIN TROUT TRCLOSE STBY V1P4 IC603 4M x 16bit SDRAM MA 0 11 DQM0 DQM1 WE CAS RAS CS BA0 BA1 SDCLK SDCKE DQ 0 15 FLASH ROM PRD PWR PCE AD 0 7 A 0 20 EEP ROM SCL SDA RS232C MTK RXD TXD X501 27MHz X TAL IC601 MT1389 DVDPLAYER ONE CHIP ...

Page 48: ...erface AUDIO Interface AUDIO MICOM IC603 SDRAM 64M DCLK WE CAS RAS CS DCKE MA 0 10 DQM0 DQM1 DQ 0 15 X501 27MHz SCL SDA Y2 Y Y3 Color Y4 Y Y5 Cb Y6 Cr ASPECT 16 9 ACLK ALRCK ABCK MUTE VSCK VSDA ASDTA 0 3 ASTB SCL SDA ASPDIF PWR PCE PRD A 0 20 AD 0 7 VFD_SCK VFD_TXD M_REQ SCKO TXDO M REQ URST S_REQ VFD_RXD ...

Page 49: ...PF Buffer IC701 Digital POWER IC IC303 Digital POWER IC IC304 Digital POWER IC CVBS COMPONENT R G B Y Pb Pr SUPER VIDEO Y C R G B Y Pb Pr Y C DAC RESET ACLK SCL SDA DAC RESET ACLK SCL SDA ADATA1 ADATA2 ADATA3 A V JACK MPEG MPEG MPEG 5 1CH BOARD FRONT R REAR R FRONT L REAR L CENTER WOOFER AUDIO L AUDIO R ADATA3 ...

Page 50: ...3 25 3 26 DVD PART SCHEMATIC DIAGRAMS MPEG SCHEMATIC DIAGRAM ...

Page 51: ...3 27 3 28 SERVO SCHEMATIC DIAGRAM ...

Page 52: ...AND MAIN FRAME SECTION A50 452 452 250 463 463 305 452 263 A47 262 A44 260 261 285 280 284 281 288 A43A 283 282 A43 A26 463 322 463 A46 TU101 463 NOTE Refer to SECTION 6 REPLACEMENT PARTS LIST in order to look for the part number of each part ...

Page 53: ...R MECH FEEDING RF 300EA 1D390 MABUCHI 015B 4560R 0008A PULLEY MOTOR 016 6871R 9294A PWB PCB ASSEMBLY TOTAL DP 9C LOADING 017 4470R 0176A GEAR DVD DP 9 LOADING MOLD 018 4974R 0067A GUIDE DVD DP 9C UP DOWN MOLD 019 3210R M008A FRAME DP 9C UP DOWN MOLD 020 3040R M066A BASE MAIN DP 9T MOLD NSP 021 4681R B009B MOTOR ASSEMBLY DECK MECHA DP9 FEEDING 024 4470R 0179A GEAR DVD DP 9 PINION MOLD 025 4470R 017...

Page 54: ... 5 1 SECTION 5 SPEAKER PART MODEL LHS T6740W 658 659 654 657 656 655 656 655 650 651 652 656 653 ...

Page 55: ... 5 2 MODEL LHS T6740C 755 756 757 755 759 758 751 750 752 754 753 752 ...

Page 56: ... 5 3 MODEL LHS T6740T 863 864 867 865 866 857 858 861 856 860 868 859 862 853 855 854 853 852 850 851 ...

Page 57: ... 5 4 MEMO ...

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