LG 75SJ857A Service Manual
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LG 75SJ857A Service Manual

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LED TV
SERVICE MANUAL
CHASSIS : UA71F
MODEL : 75SJ857A
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL69823936 (1705-REV00)
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
75SJ857A-UC

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  • 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 SOFTWARE UPDATE ................9 BLOCK DIAGRAM ................. 10 EXPLODED VIEW .................. 17 ASSEMBLY GUIDE / DISASSEMBLY GUIDE ........18 TROUBLE SHOOTING GUIDE ..........APPENDIX - 2 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 3: Safety Precautions

    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: Servicing Precautions

    - 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: Specification

    AV and DVI use same jack SPDIF out(1EA) Optical Audio out Rear (1EA), USB Input(3EA) EMF, DivX HD, For SVC (download) JPEG, MP3, DivX HD Side(1EA), Rear(2EA) - 6 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 7 UDTV 2160P 3840*2160 56.25 25.00 297.00 UDTV 2160P 3840*2160 67.5 30.00 297.00 UDTV 2160P 4096*2160 53.95 23.97 296.70 UDTV 2160P 4096*2160 UDTV 2160P - 7 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 8 296.70 UDTV 2160P 4096*2160 67.5 30.00 UDTV 2160P 4096*2160 112.5 50.00 UDTV 2160P 4096*2160 134.86 59.94 593.40 UDTV 2160P 4096*2160 60.00 UDTV 2160P - 8 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 9: Software Update

    (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 - 9 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 10: Block Diagram

    BLOCK DIAGRAM 1. SOC - 10 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 11 2. Tuner + CI - 11 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 12: Video & Audio In/Out

    3. Video & Audio IN/OUT - 12 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 13 4. HDMI 2.0 - 13 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 14 5. USB / Wi-Fi / M-Remote / UART - 14 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 15 6. I2C Map - 15 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 16 7. EPI block (PMIC) - 16 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 17: 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. Do not modify the original design without permission of manufacturer. - 17 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 18 - Unlock screw (“a”: 17EA, “b”: 1EA) to separate from module. And then separate Main Chassis & Power Chassis from module. And then separate Middle Cabinet Assy from module - 18 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 19 - Unlock screw (“e”: 10EA) and then separate each part. - Detach Tape (“f” : 2EA) Unlock screw (“e”: 2EA) and then separate each part. - 19 - Copyright © LG Electronics Inc. All rights reserved. Only for training and service purposes.

  • Page 20: Troubleshooting Guide

    TROUBLE SHOOTING GUIDE Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 21 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 22 ☞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 23 Check various Check and No Video/ Normal voltages of Power replace No audio voltage? Board (20V, 13.2V…) MAIN B/D Replace Power Board and repair parts Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 24 1. Reconnection 2. Install Booster 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 25 /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 26 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 27 Measure voltage of each output of Power B/D Normal? ※ Normal Replace Main B/D voltage? Normal Close Check ST-BY 3.5V voltage? ☞A18 Replace Power B/D Replace Power Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 28 "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 29 20V 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 30 (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 31 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 32 Replace MR13 Close Down load the Firmware * If you conduct the loop at 3times, change the M4. * INSTART MENU14.RF Remocon Test3. Firmware download Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 33 “NG”? Voltage? 1pin Main B/D ☞A24 Close Check & Repair Wifi cable connection ☞A4 Wi-Fi Mac value Close is “NG”? Change the Wifi assy Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 34 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 35 “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 36 Revised date 15/15 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 37 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 38 Voltage and speaker checking method when there is no audio Remote control operation checking method D. Function error Motion Remote operation checking method Wifi operation checking method Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 39 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 front side. Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 40 2. Enter into White Balance. 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 41 TUNER input signal strength checking method Content date <ALL MODELS>  Advanced 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 42 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 43 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 44 Revised Content Cconnection 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 45 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 46 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 47 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 48 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 49 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 50 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 51 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 52 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 53 B. Power error _No power symptom date Revised Check power input voltage and ST-BY 3.5V Content date Check the DC 13.2V line for ST-BY Voltage Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.
  • Page 54 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 55 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 56 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 57 2.Check the standby 3.5V on the terminal 16 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 58 Checking order to check motion remote/wifi ② +3.5_Wifi Checking order 1.Check BT/Wifi cable condition between BT/Wifi assy & Main board. 2.Check the 3.5V on the terminal 24 A23/A24 Copyright © 2017 LG Electronics Inc. All rights reserved. Only for training and service purposes.

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