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LG 28LM4 0B-PU Series Service Manual
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LG 28LM4 0B-PU Series Service Manual

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MFL71428602 (1902-RE00)
Any reproduction, duplication, distribution (including by way of email, facsimile or other electronic 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.
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Summary of Contents for LG 28LM4 0B-PU Series

  • Page 1 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...

  • Page 2: Table Of Contents

    CONTENTS ....................2 SAFETY PRECAUTIONS ................ 3 SERVICING PRECAUTIONS ..............4 SPECIFICATION ..................6 SOFTWARE UPDATE................8 BLOCK DIAGRAM ................. 11 EXPLODED VIEW .................. 12 DISASSEMBLE GUIDE................13 TROUBLE SHOOTING GUIDE ..............22 - 2 - 2019...
  • Page 3 Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by in the Exploded 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.

  • Page 4: Safety Precautions

    CAUTION: Before servicing receivers covered by this service 2. After removing an electrical assembly equipped with ES manual and its supplements and addenda, read and follow the devices, place the assembly on a conductive surface such as SAFETY PRECAUTIONS on page 3 of this publication. aluminum foil, to prevent electrostatic charge buildup or expo- NOTE: If unforeseen circumstances create conflict between the sure of the assembly.
  • Page 5 3. Solder the connections. Some chassis circuit boards have slotted holes (oblong) through CAUTION: Maintain original spacing between the replaced which the IC leads are inserted and then bent flat against the cir- component and adjacent components and the circuit board to cuit foil.

  • Page 6: Specification

    SPECIFICATION NOTE : Specifications and others are subject to change without notice for improvement. 1. Application range 3. Test method This specification is applied to the LED TV used 1) Performance: LGE TV test method followed MS3553T.PB791 chassis. 2) Demanded other specification NOM-001, NOM-032, NOM-192 -EMI：FCC-15/ICES-003/BETS-7 for NAFTA 2.
  • Page 7 Resolution H-freq(kHz) V-freq.(kHz) 15.73 720*480i 60.00 31.50 720*480p 60.00 1440*576i 16.63 50.00 31.50 720*576p 50.00 37.50 50.00 1280*720p 1280*720p 45.00 60.00 28.13 1920*1080i 50.00 33.75 1920*1080i 60.00 1920*1080p 56.25 50.00 67.50 1920*1080p 60.00 Resolution H-freq(kHz) V-freq.(kHz) 720*400 31.469 640*480 31.469 59.940 800*600 35.156...

  • Page 8: Software Update

    SOFTWARE UPDATE PROCEDURE 0. Reason why area code need to set when change mainboard. Area code is related with broadcast country setting of user menu. If it is applied wrong number, customer can not see own country in broadcast country list when initial set. Check Area code after change mainboard.
  • Page 9 1. USB Upgrade Check software upgrade bin file name as below.Only bin file name is the same as TV set,USB upgrade can be success. Region Model Software Name(FY2019) Nafta LM_NAF_3553.bin Need do AC on upgrade as below steps. 1. Copy the software Bin to the USB root. 2.
  • Page 10 2.AreaCode Setting Guide SETTING+1147 >Factory Settings >GENERAL SETTING >Area Option: 1.Area Code: ~3: NAFTA Region Area Code Subsidiary Main Market Sub Market LGEUS Canada Canada NAFTA LGECI Canada Canada Mexico Mexico LGEMS Mexico Mexico Mexico Mexico User can select area code by left and right key, and set area code with item “5 Set” by right and OK key. 2.LangGr.:English.

  • Page 11: Block Diagram

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  • Page 12: Exploded View

    EXPLODED VIEW IMPORTANT SAFETY NOTICE Many electrical and mechanical parts in this chassis have special safety-related characteristics. These parts are identified by the Exploded 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.

  • Page 13: Disassemble Guide

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  • Page 16 4. . Remove the screw that lock the main board after removing the mirror line and function key line. - 16 - 2019...
  • Page 17 5. Remove the tape and unplug the LVDS. - 7 - 2019...
  • Page 18 6. Remove the tape that holds the speaker line and remove the horn. - 18 - 2019...
  • Page 19 7. Remove the wall bracket. - 19 - 2019...
  • Page 20 8. . Remove the tape tha holds the IR plate line and remove the IR plate. - 20 - 2019...
  • Page 21 9. Place the removed mirror flat on the guard mat. - 21 - 2019...

  • Page 22: Trouble Shooting Guide

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  • Page 24 Standard Repair Process Established A. Video error Error date symptom No video/ Normal audio Revised date 1/13 First of all, Check whether all of cables between board is inserted properly or not. (Main B/D↔ Power B/D, LVDS or EPI Cable, Speaker Cable, IR B/D Cable,,,) Replace T-con/Main No video Normal...
  • Page 25 Standard Repair Process Established A. Video error Error date symptom No video/ No audio Revised date 2/13 Check various Check and No Video/ Normal voltages of Power replace No audio voltage? Board (12.5V…) MAIN B/D MAIN B/D Replace Power Board and repair parts - 25 - 2019...
  • Page 26 Standard Repair Process Established A. Video error Error date symptom Picture broken/ Freezing Revised date 3/13 . By using Digital signal level meter . By using Diagnostics menu on OSD Check RF Signal level ( Advanced→ Channels→ Channel Tuning→ Manual Tuning → Check the Signal ) - Signal strength (Normal : over 50%) - Signal Quality (Normal: over 50%) Check whether other equipments have problem or not.
  • Page 27 Standard Repair Process Established A. Video error Error date symptom Color error Revised date 4/13 Check and Check color by input replace Link -External Input Color Cable Color Color Replace Main B/D Replace module (EPI or LVDS error? error? error? -HDMI Cable) and contact...
  • Page 28 Standard Repair Process A. Video error Established Error date symptom Vertical / Horizontal bar, residual image, Revised date 5/13 light spot, external device color error light s pot, external d evice color e rror Vertical/Horizontal bar, residual image, light spot Replace Module Check color condition by input...
  • Page 29 Standard Repair Process Established B. Power error Error date symptom No power Revised date 6/13 DC Power on Power Normal Replace Check Check Power by pressing Power Key Power Power operation? operation? On ‘”High” On ‘ ‘ ”High” On Remote control .
  • Page 30 Standard Repair Process Established B. Power error Error date symptom Off when on, off while viewing, power auto on/off Revised date 7/13 Check outlet (If Power Off mode is not displayed) Normal Replace Main B/D Replace Main B/D Check A/C cord k A/C Error? Check P...
  • Page 31 Standard Repair Process Established C. Audio error Error date symptom No audio/ Normal video Revised date 8/13 A20+A18 Check user Check audio 12.5V No audio Normal menu > of Power Board No sound Screen normal voltage Speaker test Replace Power Board and repair parts Adjust Volume or mute to unmute Check Replace MAIN Board...
  • Page 32 Standard Repair Process Established C. Audio error Error date symptom Wrecked audio/ discontinuation/noise Revised date 9/13 → abnormal audio/discontinuation/noise is same after “Check input signal” compared to No audio A20+A18 Wrecked audio/ Check and replace Check audio Check audio Discontinuation/ speaker and B+ Voltage (12.5V) Noise for...
  • Page 33 Standard Repair Process D. Function error Established Error date symptom Remote control & Local switch checking Revised date 10/13 1. Remote control(R/C) operating error Replace Main B/D Check & Repair Check R/C itself Check R /C itself Normal Normal Normal Normal Check B+5V Check B...
  • Page 34 Standard Repair Process Established D. Function error Error date symptom External device recognition error Revised date 11/13 Check technical Check technical Check information Technical External Input and Signal input Replace Main B/D information? input? - Fix information Component signal Recognition error - S/W Version HDMI/ HDMI/...
  • Page 35 Standard Repair Process Established E. Noise Error date symptom Circuit noise, mechanical noise Revised date 12/13 Identify Check Circuit nose location of Replace 3in1 board noise type noise Mechanical Check location of noise noise When the nose is severe, replace the module Mechanical noise is a natural (For models with fix information, upgrade the phenomenon, and apply the 1st level...
  • Page 36 Standard Repair Process Established F. Exterior defect Error date symptom Exterior defect Revised date 13/13 Zoom part with Module Replace module damage exterior damage Cabinet Replace cabinet damage Remote control Replace remote control damage Stand dent Replace stand 2019 - 36 -...
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  • Page 39 <28”> After turning on the power and disassemblin After turning on the power and disassembling g the case, check with the naked eye, the case, check with the naked eye, whether whether you can see light from locations. you can see light from locations. - 39 - 2019...
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  • Page 43 <28”> Checking method: 1. Check the signal strength or check whether the screen is normal when the external device is connected. 2 2 . A A ft fter measuri i ng each h volt ltage f f rom power suppl l y, fi finall lly repl l ace t t h h e M M AIN AIN B B OARD OARD.
  • Page 44 <28”> 2019 - 44 -...
  • Page 45 <28”> Check the contact condition of the Link Cable, especially dust or mis insertion. 2019 - 45 -...
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  • Page 58 Standard Repair Process Detail Technical Manual Error Established B. Power error _No power symptom date Revised Check power input voltage Content date date Backlight Values Forward Symbol Unit Voltage 31 5 31.5 34.8 37.8 40.8 69.6 75.6 81.6 <28”> Check the DC 12V. - 58 -...
  • Page 59 <ALL MODELS> 1. . Press the Setti button on the remote control 2. . Select the Soun function of the Menu 3. . Select the “Speake test” 4. You can listen the sound 2019 - 59 -...
  • Page 60 Standard Repair Process Detail Technical Manual Error Established C. Audio error_No audio/Normal video symptom date Revised Voltage and speaker checking method Content date date when there is no audio when there is no audio ① ① ② ② ② SPK_R+FT <28”>...
  • Page 61 Standard Repair Process Detail Technical Manual Error Established D. Function error symptom date Revised Content Remote control operation checking method Remote control operation checking method date date Pin name ① IR Sensor &  Keypad & LED Rear Front ③ PIN1 ② Checking order to check remote control Checking order to check remote control Checking order 1.Check IR cable condition between IR &...
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  • Page 64 P-ONLY Factory mode Input Source chagne INPUT Ex)HDMI, USB, Component POWER Power on/off Sound Test Ex)Sound 100, 80, 50, 0 Changes Picture Mode Changes Sound Mode changes Stereo mode Green Eye test OSD Green Eye value display TV set information IN START Model, S/W version, results Adjust menu...
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  • Page 67 Check software upgrade bin file name as below.Only bin file name is the same as TV set,USB upgrade can be success. Region Model Software Name(FY2019) Nafta LM_NAF_3553.bin Need do AC on upgrade as below steps. 2019 - 67 -...
  • Page 68 Upgrading: Upgrade succeed: Upgrade succeed: 2019 - 68 -...

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