LG 28LJ400B Service Manual Download Page 29 | Manualshive

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A5 Power circuit diagram

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Power circuit diagram

AC

input

EMI

filter

Rectifie

AC/DC

Power convertor

19V/24V/
32V/50V

output

Output

filter

Output

filter

19V/24V/

32V/50V

output

12V

output

Feed

back

power amplifier

ǃ

The main IC

ǃ

Screen voltage

and so on

LED driver

LED

VCC_Panel

PWM_DIM

Copyright

ⓒ

2017 LG Electronics Inc. All rights reserved.

Only training and service purposes.

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Summary of Contents for 28LJ400B

Page 1: ... means publication modification copying or transmission of this Service Manual is STRICTLY PROHIBITED unless you have obtained the prior written consent of the LG Electronics entity from which you received this Service Manual The material covered by this prohibition includes without limitation any text graphics or logos in this Service Manual Copyright ⓒ 2017 LG Electronics Inc All rights reserved...

Page 2: ...d Only training and service purposes CONTENTS CONTENTS 2 SAFETY PRECAUTIONS 3 SERVICING PRECAUTIONS 4 SPECIFICATION 6 SOFTWARE UPDATE PROCEDURE 8 BLOCK DIAGRAM 10 EXPLODED VIEW 12 DISASSEMBLE 13 TROUBLE SHOOTING GUIDE APPENDIX ADJUSTMENT INSTRUCTION APPENDIX ...

Page 3: ... such as antennas terminals etc to be sure the set is safe to operate without damage of electrical shock Leakage Current Cold Check Antenna Cold Check With the instrument AC plug removed from AC source connect an electrical jumper across the two AC plug prongs Place the AC switch in the on position connect one lead of ohm meter to the AC plug prongs tied together and touch other ohm meter lead in ...

Page 4: ... charge on your body by touching a known earth ground Alter natively obtain and wear a commercially available discharg ing wrist strap device which should be removed to prevent potential shock reasons prior to applying power to the unit under test 2 After removing an electrical assembly equipped with ES devices place the assembly on a conductive surface such as aluminum foil to prevent electrostat...

Page 5: ...joints of the two original leads If they are not shiny reheat them and if necessary apply additional solder Fuse and Conventional Resistor Removal Replacement 1 Clip each fuse or resistor lead at top of the circuit board hollow stake 2 Securely crimp the leads of replacement component around notch at stake top 3 Solder the connections CAUTION Maintain original spacing between the replaced componen...

Page 6: ...owed each drawing and specification by part number in accordance with BOM 5 The receiver must be operated for about 5 minutes prior to the adjustment 3 Test method 1 Performance LGE TV test method followed 2 Demanded other specification Safety CB IEC specification EMC CE IEC CISPR 4 Model General Specification No Item Specification Remarks 1 Receiving System NTSC M ATSC 2 Promramme coverage 1 VHF ...

Page 7: ...80 31 469 59 940 3 800 600 35 156 56 250 4 800 600 37 879 60 317 5 1024 768 48 363 60 004 6 1280 720 45 0 60 0 5 1280 768 47 776 59 870 6 1366 768 49 1 60 0 DTV 1 640 480p 31 47 59 94 2 640 480p 31 5 60 00 3 720 480p 31 47 59 94 4 720 480p 31 5 60 00 5 1280 720p 44 96 59 94 6 1280 720p 45 00 60 00 7 720 1440 480i 15 73 59 94 8 720 1440 480i 15 75 60 00 9 720 576p 31 25 50 00 10 1280 720p 37 5 50 0...

Page 8: ... 1 USB Upgrade 1 Place the higher version software in LG_DTV folder in USB root folder like this 2 Plug in USB disk then a notify OSD will be displayed if the software in LG_DTV higher than current software of TV set 3 Select YES button and press OK key if you want to update TV software the update OSD will be displayed ...

Page 9: ...t after update success 2 AC ON In order to avoid the software which is on the mainboard can not work normal for current panel you can upgrade the correct software through AC ON 1 Copy the Software Bin to the U Disk root 2 Insert the U Disk to the mainboard USB Port 3 The AC on 4 Then the TV will upgrade and need to reboot after upgrade success Upgrading Red 1000ms Green 1000ms alternates the TV se...

Page 10: ...IAGRAM YPBPR CVBS Audio IN Optical MSD3553 HDMI1 HDMI2 NTSC ATSC I2C AGC VIF USB 2 0 LVDS miniLVDS SPI FLASH AMP TPA5733l L R I2S IR KEY DDR3 128MB Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 11: ...1 DC DC 2000mA MP9495 5V_STB 800mA eff 90 1730mA Add_W 0xC0 LVDS Add_R Add_W 1000mA VCC PANEL TAS5733L TBD U1 MSD3553 150mA U1 MSD3553 700mA D LDO UL1 VCC_DDR 230mA 230mApeaU k 1 MSD3553 120mAavg USB2 0 1000mA 500mA 8ohm 5W POW_EN POW_EN 800mA D LDO UL1 3V3_M 270mA 270mA UT2 Tuner 200mA U1 TAS5733 68mA UA1 TAS5733 Addr 0x56 Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and ...

Page 12: ...ed View It is essential that these special safety parts should be replaced with the same components as recommended in this manual to prevent Shock Fire or other Hazards Do not modify the original design without permission of manufacturer Copyrightⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes 200 120 540 541 542 400 510 840 905 900 LV1 700 AR1 ARC1 ...

Page 13: ...FNCMF 13 1 1 Rated regulations WEEE directive EPEAT Fig 0 Picture of front side Fig 1 Put the MNT on the clean vinyl Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 14: ... By using screw driver and disassemble the stand body Fig 3 unlock the back cover Screw 11 EA By using screw driver and disassemble the back cover Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 15: ... 15 Fig 4 Disassemble BTM IO Cover and SIDE IO Cover Fig 5 Disassemble all Plugs Marked in red Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 16: ... the Power board Screw 4 EA By using screw driver and disassemble the Power board Fig 7 Disassemble the LVDS then take it away Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 17: ... 17 Fig 8 Remove all adhesive tapes Fig 9 Remove the Speaker and Lens Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 18: ... Hanging Screw 2 EA By using screw driver and disassemble the Hanging Bracket Fig11 unlock the PCBA Screw 3 EA By using screw driver Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 19: ... 19 Fig 12 Disassemble the Front Cabinet Fig 13 Disassemble the OC Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 20: ...e Panel and Films Fig 15 unlock the Light bar Screw 9 EA By using screw driver and disassemble the Reflector Fig 16 Disassemble Light bar Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 21: ... 7 HDMI YPbPr CVBS error A4 2 8 Power circuit diagram A5 9 Power supply Trouble 2 No power A6 10 Power supply for LED drive No backlight A7 13 Exchange Module itself 1 Appendix 1 14 Exchange Module itself 2 Appendix 2 1 1 5 Appendix ADJUSTMENT INSTRUCTION ADJUSTMENT Appendix 3 Display Trouble Function error Appendix Defected Type caused by T Con Module Copyright ⓒ 2017 LG Electronics Inc All right...

Page 22: ... board Repair the power board Y Check U2 for 5V_STB UL1 for 3 3V_STB and UD1 for 1 15V_STB Y Y Repair the abnormal circuit 1 5V_STB check U2 2 3 3V_STB check UL1 3 1 15V check UD1 and peripheral components N Power on check QM32 for 5V_M UL1 for VCC_DDR Y Repair the abnormal circuit 1 5V_M heck power supply and QM32 circuit 2 CC_DDR check UL1 OK Copyright ⓒ 2017 LG Electronics Inc All rights reserv...

Page 23: ...urred screen Check if the cable is correct and connected tightly Check if the panel is OK Change the cable for panel Y N Change panel N Y Check if the output circuit from U1 MSD3553 to the jack is normal Y N Software error or U1 MSD3553 damage Repair this circuit Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 24: ... ǃDisplay Trouble white screen White screen Check if the voltage of panel power supply is normal depend on panel N Y Check the circuit of QM1 Check output signal from U1 MSD3553 Change the panel or the cable to panel Change U1 MSD3553 Y N Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 25: ...m 2016 12 31 4ǃ ǃDisplay Trouble black screen Black screen N Y Repair the circuit Check if the power supply for inverter is normal Check the inverter board Check if the control circuit between PWM_DIM and PWM ADJ is normal Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 26: ...ply circuit Y Check if PIN24 PIN31 of the AMP chip voltage is normal Check the control circuit Check the input signal Check the circuit from AMP to the jack Check the output signal Check the circuit from U1 to AMP Check the circuit between output jack and AMP chip Change AMP chip N N N N Y Y Y Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 27: ...TV can t search any channel no picture 6ǃFunction Trouble TV video Check input RF signal Check the RF source Check tuner power Check power supply circuit Check if IIC work Check IIC circuit Check IFP IFN output signal Check tuner and peripheral components Check the circuit from tuner to U1 MSD3553 N Y N N N Y Y Y 2017 ...

Page 28: ... 12 31 HDMI YPbPr CVBS 7ǃFunction Trouble HDMIǃYPbPrǃCVBS Check the signal at the jack Check the external source Check the signal on the Corresponding of U1 Check the circuit from jack to U1 MSD3553 Change U1 MSD3553 N Y N Y Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 29: ...ram AC input EMI filter Rectifie AC DC Power convertor 19V 24V 32V 50V output Output filter Output filter 19V 24V 32V 50V output 12V output Feed back power amplifierǃ The main ICǃ Screen voltage and so on LED driver LED VCC_Panel PWM_DIM Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 30: ... rectifier Check if output short Check if RB100 RB101 RB102 open Non output IR indicator light slake Check if 12Vǃ19V 24V 32V 50V output normal Check if EB1 voltage about 2Vac Y Check if UB101 PIN5 voltage is about 15V Change damaged components Change short components Change damage resistors Change UB101 9ǃPower Supply Trouble 2 N Y Y Y Y Y Y N N N N N Copyright ⓒ 2017 LG Electronics Inc All right...

Page 31: ...ut backlight slake Check if LED output cable is connect correction Y Check QB801 DB801 damage or not Remove short open status Change UB801 10ǃPower supply for LED drive Y N Y Y Y Y N N N Increase brightness check if Sampling resistor is right Y check is part of the brightness is in dim status check is all of the brightness is in dim status Check if UB801 PIN1 voltage is about 12V Copyright ⓒ 2017 ...

Page 32: ...he Module 1 Press damage Crosstalk Press damage Un repairable Cases In this case please exchange the module Crosstalk Press damage Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 33: ... HIHFW 9HUWLFDO ORFN 6RXUFH 7 HIHFW RUL RQWDO ORFN DWH 7 HIHFW RUL RQWDO OLQH DWH 7 HIHFW DWH 7 HIHFW RUL RQWDO ORFN DWH 7 HIHFW SSHQGL FKDQJH WKH 0RGXOH 8Q UHSDLUDEOH DVHV Q WKLV FDVH SOHDVH H FKDQJH WKH PRGXOH Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 34: ...RAL SETTING General setting 7 PANEL SETTING Change panel parameters Don t touch 8 EMC SETTING Some settings may affect EMC Don t touch 9 SYSTEM INFO System parameter 10 BOARD INIT Factory reset Don t touch 11 SW UPGRADE Software upgrade 13 LG SYSTEM INFO System parameter for LGE Detail 2 14 LG EZ ADJUST LG EZ adjust Detail 3 Bin Name the name of current bin name Soft Version the version of the cur...

Page 35: ...pendix ADJUSTMENT INSTRUCTION 2 LG SYSTEM INFO LG SYSTEM INFO Display some system parameters no adjustable items Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 36: ...Appendix ADJUSTMENT INSTRUCTION 3 LG EZ ADJUST Area Option Select Area USA Mexico Canada Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 37: ...DJUSTMENT INSTRUCTION Output Operation Guide SHIPPING INIT Press Right key to execute TV initialization TV will be reset Copyright ⓒ 2017 LG Electronics Inc All rights reserved Only training and service purposes ...

Page 38: ......

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