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LG 49LJ55 Series Service Manual

Chassis : la75m
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LED TV
SERVICE MANUAL
CHASSIS : LA75M
MODEL : 49LJ55**
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL69963003 (1703-REV01)
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.
Copyright © 2017 LG Electronics Inc. All rights reserved. Only training and service purposes.
CONFIDENTIAL
49LJ55**-U*

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Summary of Contents for LG 49LJ55 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 Manual.
  • Page 2 SPECIFICATION ..................6 SOFTWARE UPDATE ................8 BLOCK DIAGRAM ................... 9 EXPLODED VIEW .................. 10 DISASSEMBLY GUIDE ................12 TROUBLE SHOOTING GUIDE ..........APPENDIX - 2 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 3 When the exposed metal has no return path to the chassis the reading must be infinite. An other abnormality exists that must be corrected before the receiver is returned to the customer. - 3 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 4 - 4 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 5 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. - 5 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 6 1) Temp : 0 ~ 40 deg 2) Humidity : ~ 80 % Storage Environment 1) Temp. : -20 ~ 60 deg 2) Humidity : ~ 85% - 6 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 7 33.71 29.97 74.176 HDTV 1080P 1920*1080 33.75 30.00 74.25 HDTV 1080P 1920*1080 67.43 59.94 148.352 HDTV 1080P 1920*1080 67.50 60.00 148.50 HDTV 1080P - 7 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 8 (8) After TV turned on, Check the updated SW Version and Tool Option (6) Turn OFF the TV and On. Check the updated SW Version and Tool Option - 8 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 9 BLOCK DIAGRAM - 9 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 10 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. - 10 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 11 EXPLODED VIEW(MODULE) IMPORTANT NOTICE MRC use only * MRC : Module Repair Center - 11 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 12 Total Screw No.: 10ea 1. After Screw Disassemble, please remove B/C from Module Screw : 15 ea [Fig.1] 2. Detach Tape Detach tape [Fig.2] - 12 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 13 3. Remove all sort of cable [Fig.3] 4. IR assy, WiFi PCB assy disassembly Disassemble screw (1ea) and Remove IR cable Remove wi-f i cable [Fig. 4] - 13 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 14 5. Screw disassembly Screw : 9 ea [Fig.6] 6. Speaker disassembly (Disassemble ⓑ→ⓐ) [Fig.7] - 14 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 15 8. Screw disassembly ⓐ Disassemble squence ⓐ→ⓑ) Screw : 4ea [Fig.8] ⓑ - 15 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 16 TROUBLE SHOOTING GUIDE Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 17 E. Noise Circuit noise, mechanical noise F. Exterior error Exterior defect First of all, Check whether there is SVC Bulletin in GSCS System for these model. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 18 ☞A4 & A2 Always check & record S/W Version and White Replace Main Board Re-enter White Balance value Balance value before replacing the Main Board Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 19 ☞A18 Check various Check and No Video/ Normal voltages of Power replace No audio voltage? Board (13V…) MAIN B/D Replace Power Board and repair parts Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 20 S/W Version Picture? Bulletin? 1. Reconnection S/W Upgrade Contact with signal distributor Normal or broadcaster (Cable or Air) Picture? Normal Picture? Replace Main B/D Close Close Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 21 /Cable device and error normal cable Request repair for external device/cable Check external External device device and Replace Main/T-con B/D HDMI /Cable cable error normal Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 22 Replace screen? Screen (Check normal operation of Main /T-con External Input, Component, normal? RGB and HDMI/DVI by connecting Jig, pattern Generator ,Set-top Box etc. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 23 Measure voltage of each output of Power B/D Normal? Normal Replace Main B/D voltage? Normal Close Check ST-BY 7.8V voltage? ☞A18 Replace Power B/D Replace Power Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 24 "POWEROFF_UNKNOWN" Power off by unknown status except listed case "POWEROFF_ABNORMAL1" Power off by abnormal status except CPU trouble Abnormal "POWEROFF_CPUABNORMAL" Power off by CPU Abnormal Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 25 13V of Power Screen normal voltage Speaker off Board Cancel OFF Replace Power Board and repair parts Check Replace MAIN Board Disconnection Speaker disconnection Replace Speaker Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 26 (In case of Connect and check Normal External Input other external audio? signal error) device Check and fix external device Check and fix external device Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 27 Replace Main B/D (Power B/D don’t have problem) If R/C operate, Normal Close operating? Explain the customer cause is interference from light in room. Replace R/C Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 28 “NG”? Voltage? 1pin Main B/D ☞A24 Close Check & Repair Wifi cable connection ☞A4 Wi-Fi Mac value is “NG”? Close Change the Wifi assy Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 29 Recognition error - S/W Version HDMI/ Check and fix Replace Main B/D DVI, Optical Fix in external device/cable Recognition error accordance with technical information Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 30 “Part related to nose” in the Owner’s then proceed as shown in the solution manual Manual. (For models without any fix information, provide the description) Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 31 Revised date 16/16 Zoom part with Module Replace module exterior damage damage Cabinet Replace cabinet damage Remote Replace remote control control damage Stand Replace stand dent Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 32 Defected Type caused by T-Con/ Exchange Power Board (PSU) A-3/5 Inverter/ Module Exchange Module (1) A-4/5 Exchange Module (2) A-5/5 Continue to the next page Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 33 C. Audio error_ No audio/Normal video Voltage and speaker checking method when there is no audio Remote control operation checking method D. Function error Wifi operation checking method Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 34 Check LCD back light with naked eye Content date After turning on the power and disassembling the case, check with the naked eye, whether you can see light from locations. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 35 2. Enter into White Balance of item 10. 3. After recording the R, G, B (GAIN, Cut) value of Color Temp (Cool/Medium/Warm), re-enter the value after replacing the MAIN BOARD. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 36 <ALL MODELS>  All Setting  Channels Channel Tuning Manual Tuning When the signal is strong, use the attenuator (-10dB, - 15dB, -20dB etc.) Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 37 Version checking method Content date <ALL MODELS> 1. Checking method for remote control for adjustment Version Press the IN-START with the remote control for adjustment Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 38 1. Check the signal strength or check whether the screen is normal when the external device is connected. 2. After measuring each voltage from power supply, finally replace the MAIN BOARD. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 39 Revised Content Connection diagram (1) date <ALL MODELS> As the part connecting to the external input, check the screen condition by signal Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 40 Revised Content Check Link Cable(VX1) reconnection condition date <ALL MODELS> Check the contact condition of the Link Cable, especially dust or mis insertion. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 41 You can view 6 types of patterns using the ADJ Key Checking item : 1. Defective pixel 2. Residual image 3. MODULE error (ADD-BAR,SCAN BAR..) 4.Video error (Classification of MODULE or Main-B/D!) Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 42 Abnormal Power Section Solder defect, CNT Broken Solder defect, CNT Broken T-Con Defect, CNT Broken Abnormal Power Section Solder defect, Short/Crack Solder defect, Short/Crack A - 1/5 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 43 Abnormal Power Section Abnormal Power Section Solder defect, Short/Crack Abnormal Display Fuse Open, Abnormal power section Solder defect, Short/Crack Noise GRADATION GRADATION A - 2/5 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 44 Appendix : Exchange Power Board (PSU) No Light Dim Light Dim Light Dim Light No picture/Sound Ok A - 3/5 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 45 Appendix : Exchange the Module (1) Press damage Press damage Press damage Un-repairable Cases In this case please exchange the module. Crosstalk Crosstalk A - 4/5 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 46 Gate TAB IC Defect Un-repairable Cases In this case please exchange the module. Horizontal Block Gate TAB IC Defect Gate TAB IC Defect A - 5/5 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 47 Established B. Power error _No power symptom date Revised Content Check front Power Indicator date ST-BY condition: On or Off Power ON condition: Turn Off Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 48 Check power input voltage and ST-BY 3.5V Content date Values Backlight Symbol Unit Forward Voltage Check the DC 13.2V. 43LJ5500-UA 65.94 72.45 49LJ5500-UA 113.4 122.4 55LJ5500-UA 125.2 127.2 142.4 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 49 POWER OFF MODE checking method date <ALL MODELS> Entry method 1. Press the IN-START button of the remote control for adjustment 2. Check the entry into adjustment item 3 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 50 1. Press the Setting button on the remote control 2. Select the Sound function of the Menu 3. Select the Sound Out 4. Select TV Speaker Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 51 3.Connect the tester RX1 to the speaker terminal and if you hear the Chik Chik sound when you touch the GND and output terminal, the speaker is normal. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 52 2.Check the standby 3.5V on the terminal 22 pin (③) 3.AS checking the Pre-Amp(IR LED light) , the power is in ON condition, an Analog Tester needle should move slowly, otherwise, it’s defective. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 53 KEY2 Checking order to check WiFi KEY1 Checking order 1.Check IR/Wifi cable condition between Wifi assy & Main board. 2.Check the 3.5V on the terminal Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.

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