42LN5300 backlight randomly blacks out

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  • howardc64
    Badcaps Veteran
    • Jun 2017
    • 492
    • United States

    #1

    42LN5300 backlight randomly blacks out

    Have sound. tried 2 main boards with same symptom (so likely ruled out main board for sure)

    - Whenever backlight goes out, it is always recoverable by disconnect LED from PSU, test with LED tester, reconnect LED to PSU. Turn on TV. Without using LED tester, blacklight remains out.

    - When backlight is on and run white image test, shows no burnt out LEDs (see attached, uneven bright spot on the right center isn't really as visible as the pic)

    Seems pretty definitive there are weak LED(s) in the array and LED tester's gradual voltage ramp makes it work again for awhile. Thought I ask other's experiences before buying the LEDs. Thanks
    Attached Files
  • neilc6
    Badcaps Legend
    • Nov 2015
    • 1550
    • Canada

    #2
    Re: 42LN5300 backlight randomly blacks out

    Backlight issues are almost always the LEDs themselves especially LN, LA, LB or LF series. When intermittent, the voltage can fluctuate and trip the protection circuitry. One bad LED you may not be able to see on a white screen. Just replace them all with new and turn down the backlight level on all inputs. Just picked up a 42LN5700 with cracked screen for parts. Owner said he loved the TV and replaced the backlights previously. Curious, I checked his work and he didn't do a full replacement and had 2 strips that were original and one of them had a shorted LED. He also never removed the standoffs so the reflector sheet was floating and causing shadows. https://techhometravel.com/lg-ln-ser...ed-backlights/
    Last edited by neilc6; 07-06-2022, 09:12 AM.

    Comment

    • alfatv
      Badcaps Veteran
      • Sep 2020
      • 353
      • Canada

      #3
      Re: 42LN5300 backlight randomly blacks out

      The least hassle is to replace all LED strips.
      It could be also bad contact or intermittent LED, that you need to figure it out by yourself.

      Comment

      • howardc64
        Badcaps Veteran
        • Jun 2017
        • 492
        • United States

        #4
        Re: 42LN5300 backlight randomly blacks out

        Thanks. Will replace LED strips, test, and report back.

        Comment

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