LG 75SM9900PTA Service Manual
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LG 75SM9900PTA Service Manual

Chassis ub91l
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LED TV
SERVICE MANUAL
CHASSIS : UB91L
MODEL : 75SM9900PTA
CAUTION
BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.
P/NO : MFL71455901 (1907-REV00)
Copyright © 2019 LG Electronics Inc. All rights reserved. Only training and service purposes.
CONFIDENTIAL

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  • Page 1 LED TV SERVICE MANUAL CHASSIS : UB91L MODEL : 75SM9900PTA CAUTION BEFORE SERVICING THE CHASSIS, READ THE SAFETY PRECAUTIONS IN THIS MANUAL. P/NO : MFL71455901 (1907-REV00) Copyright © 2019 LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 2 SOFTWARE UPDATE ................10 BLOCK DIAGRAM ................. 11 EXPLODED VIEW .................. 12 DISASSEMBLY GUIDE / ASSEMBLY GUIDE ........14 TROUBLE SHOOTING GUIDE ..........APPENDIX - 2 - Copyright © LG Electronics Inc. All rights reserved. Only 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 training and service purposes.

  • Page 4: Servicing Precautions

    - 4 - Copyright © LG Electronics Inc. All rights reserved. Only 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 training and service purposes.

  • Page 6: Specification

    DVI Audio, Component, AV 10 SPDIF out Optical Audio out Head phone out Antenna, HDMI1, HDMI2, HDMI3, HDMI4 USB1, USB2, USB3 Except UB93x 12 Ethernet Connect - 6 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 7: Component Input

    HDTV 1080P 1920*1080 33.71 29.97 79.12 HDTV 1080P 1920*1080 33.75 79.2 HDTV 1080P 1920*1080 56.25 148.5 HDTV 1080P 1920*1080 67.43 59.94 148.35 HDTV 1080P - 7 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 8 107.89 23.98 1188 7680*4320 1188 7680*4320 1188 7680*4320 131.87 29.97 1188 8K Model Only. 7680*4320 1188 7680*4320 2376 7680*4320 263.74 59.94 2376 7680*4320 2376 - 8 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 9 UDTV 2160P 4096*2160 112.5 UDTV 2160P 4096*2160 134.86 59.94 593.4 UDTV 2160P 4096*2160 UDTV 2160P 2560*1440 88.78 241.5 UHD 60Hz 2560*1440 497.7 UHD 120Hz - 9 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 10: Usb Download

    (7) Click [Yes] : TV will be DC OFF → ON. and Tool Option (8) After TV turned on, Check the updated SW Version and Tool Option. - 10 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 11: Block Diagram

    BLOCK DIAGRAM - 11 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 12: 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. - 12 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 13 EXPLODED VIEW (CABLE) - 13 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 14 (remove direction : under → upper) (remove direction : under → upper) Right Left Hera Hera Hera Hera Hera Hera <Step2> <Step1> <Step3> <Step3> <Step1> <Step2> - 14 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 15 Hera (6) Two people grasp B/C, and remove B/C. (Grasp position : 600~800mm) (7) B/C Handling is refer to B/C Handling Guide. <Step1> <Step2> - 15 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 16 - Stand and Top middle Shoulder width 600mm Grasp. (UF85 Applied method) - 2 people set up : 4-corner Handling ▪ Two people Handling Guide (NG) - 16 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 17 (3)Assemble the Screw of B/C and Stand. 75SM90 Stand Screw : 4 Point 75SM90 Holder 10 Points 75SM90 Screw 16 Points 75SM90 Latch 3 Points - 17 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 18 P1400 P402 P401 P203(14P) P700 CN101 P202 P7602 P7601 P1401 CN102 P202 P501 P5901/2/3 P500 P503 P502 P202(15P) (remove cables from the supporter holder) - 18 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 19 (4) Screw disassembly Screw point (5) Speaker disassembly (6) Stand Supporter disassembly Screw point - 19 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 20: Disassembly Guide

    * Reuse it when assemble it. * Disassemble the Screws (Except for 5 screws) (3) Disassemble of Case Top screws. bottom side screws 6 EA - 20 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 21 (6) Disassemble Hooks. (UP 2 EA, Left/Right each 1 EA) About 340mm About 340mm (7) Panel and Guide Panel disassembly (use adsorber) * 12 Point adsorber - 21 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 22 *Be careful not to damage the reflector sheet (11) Removal of LED Array *Press the CNT of extension B/D and then remove the LED array at an angle - 22 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 23: Assembly Guide

    * Assemble the reflector sheet bellow the lens with your fingers * In the case of corner and center, place the side marked UP on top. (3) Assemble the DPS(28 EA). - 23 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 24 (7) Tighten the screws from back side(5 points) and bottom side of guide panel * Remove the fixed tape first, then assemble the case top - 24 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.
  • Page 25 *Then assemble T-Con FFC and Cover shield (10) Assemble the guide panel. * Assemble the Screws UP L/R Down L/R * Assemble Pad of 4Corner (Reuse). - 25 - Copyright © LG Electronics Inc. All rights reserved. Only training and service purposes.

  • Page 26: Troubleshooting Guide

    TROUBLE SHOOTING GUIDE Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 27 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 28 ☞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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 29 ☞A9 Check various Check and No Video/ voltages of Power Normal replace No audio Board (12V…) voltage? MAIN B/D Replace Power Board and repair parts Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 30 1. Reconnection 2. Install Booster S/W Upgrade Contact with signal distributor Normal Picture? or broadcaster (Cable or Air) Normal Picture? Replace Main B/D Close Close Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 31 Replace Main/T-con B/D Component device/Cable cable error normal Request repair for external device/cable Check external External HDMI device and Replace Main/T-con B/D device/Cable error cable normal Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 32 Replace (Check normal operation of HDMI/ Screen Main /T-con External Input, Component, normal? RGB and HDMI/DVI by connecting Jig, pattern Generator ,Set-top Box etc. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...

  • Page 33: Power Error

    Measure voltage of each output of Power B/D Normal? Normal Replace Main B/D voltage? Normal Close Check ST-BY 3.5V voltage? ☞A9 Replace Power B/D Replace Power Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 34 Normal Replace Main B/D Check Power B/D voltage? voltage ※ Caution Check and fix exterior Replace Power B/D of Power B/D Part Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 35 Reboot by SW down load function UNKNOWN No meaning (same as initial value) COMP_END OLED threshold voltage degradation(Compensation) completes. PNWASHDONE Power off by panel noise wash function complited. (OLED) Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 36 Screen normal of Power Board voltage Speaker off Cancel OFF Replace Power Board and repair parts Check Speaker Replace MAIN Board Disconnection disconnection Replace Speaker Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 37 (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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...

  • Page 38: Function Error

    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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 39 Replace MR19 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 40 Voltage? +3.5V_WiFi INSTART menu Main B/D ☞A15 Close Check & Repair Wifi cable connection ☞A4 Wi-Fi Mac value Close is “NG”? Change the Wifi assy Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 41 Recognition error - S/W Version HDMI/ Check and fix DVI, Optical Replace Main B/D Fix in external device/cable Recognition accordance error with technical information Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 42 “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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 43 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 44 A-6/11 ~ 8/11 Defected Type caused by T-Con/ Module A-9/11 ~ Exchange T-Con (1) ~ (2) 10/11 Exchange Power Board(PSU) A-11/11 Continue to the next page Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 45 Check items after Main B/D replacement E. Etc Adjustment Test pattern - ADJ Key How to use JIG (Power B/D Diagnostic Smart Jig Multi Gender) Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 46 Check Back Light On with naked eye Content date If the Black light LED assemble is „OK‟, you can see the lights on each points. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 47 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 48 All settings  Programmes  Programme Tuning & settings  Manual Tuning When the signal is strong, use the attenuator (-10dB, -15dB, -20dB etc.) Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 49 Revised Content Version checking method date 1. Checking method for remote control for adjustment Version Press the IN-START with the remote control for adjustment Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 50 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 51 Revised Content Connection diagram date As the part connecting to the external input, check the screen condition by signal Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 52 A. Video error_Color error symptom date Revised Content Check Link Cable(VX1) reconnection condition date Check the contact condition of the Link Cable, especially dust or mis insertion. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 53 Screen darkness to disconnection of the FFC cable pin. G color transient due to poor FFC cable CABLE G Color Excessive connection A - 1/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 54 LVDS cable connection problem CABLE Color spread LVDS cable connection problem Due to foreign substance withi nLVDS CABLE Screen stop cable PIN A - 2/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 55 Main IC problem Main Dark picture Dark left-side screen Top/bottom screen part Main Broken picture Picture problem due to tuner Inner side quality problem A - 3/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 56 Screen spread Screen corner appears blurry Main Color Spread Color spread on the screen Main Blurry Screen Blurry picture on the screen A - 4/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 57 Screen picture spread problem Screen problem No problem at the initial stage. Right-side Main During Heat run, right-side picture picture problem problem A - 5/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 58 BLU internal foreign matter inflow MODULE Internal matter 6 block image broken MODULE Image broken MODULE Image broken Screen sync signal broken A - 6/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 59 BLU Vertical spreading on cube screen in no MODULE Vertical smear signal MODULE Over color Screen contour part brightly Over color A - 7/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 60 Center of the screen 1 block dark MODULE Screen darkness MODULE Vertical bar Center Vertical Bar Darkness at the MODULE bottom of the MODULE internal BLU breakage screen A - 8/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 61 T-Con is defective and the picture below T-CON image broken the screen is broken A - 9/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 62 The entire screen is dark and bit noise T-CON Image Broken occurs The entire screen is dark and bit noise T-CON Image Broken occurs A - 10/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 63 Appendix : Exchange Power Board (PSU) #11 Check parts by symptom No Light No picture/Sound Ok A - 11/11 Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 64 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 65 Voltage Rated Current [A] Variable range [V] (J42/J43/J44) 61.2V (57.1V ~ 73.7V) 3.6A (0~3.6A) PWR_ON (J50) SK100 (AC input) All condition meets, Power Board OK. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 66 LED blank 7 times Local data error (Checksum & Data Length) Edge, Slim Direct V-sync signal error LED blank 8 times V-sync signal is low Edge, Slim Direct Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 67 POWER OFF MODE checking method date Entry method 1. Press the IN-START button of the remote control for adjustment. 2. Check the entry into adjustment item 3. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...

  • Page 68: Checking Method

    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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 69 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 70 2. Check the standby 3.5V on the terminal (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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 71 Checking order to check motion remote/wifi Checking order 1. Check BT/Wifi cable condition between BT/Wifi assy & Main board. 2. Check the 3.5V on the terminal 1 pin. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 72 Standard Repair Process Detail Technical Manual Error Established E. Etc. symptom date Revised Content How to use the Service remote control date 1. How to access the remote control Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 73 Digital EYE function ON/OFF For some Model, access to the Test Pattern TILT Used for screen tilting change (Access to the old PDP control mode) Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 74 Connects to external input 1,2,3 COMP1,2 (Added function) Connects to Component 1,2 HDMI1,2,3,4 Connects to HDMI 1,2,3,4 (Add function) DVI (Add function) Connects to DVI Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 75 - Record the R, G, B (GAIN, Cut) value of the color temperature before main board replacement. After replacing the main board, key in the recorded value. Copyright © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...
  • Page 76 You can view 11 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 © 2019 LG Electronics. Inc. All rights reserved. Only for training and service purposes...

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