Philips 49PUT4900/12 no backlight

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  • Repair_dane
    Member
    • May 2020
    • 42
    • Danmark
    #1

    Philips 49PUT4900/12 no backlight

    Hi guys,

    tv turns on and works as usual, but without any backlights.
    LED-tester shows that the LEDs seem to work fine (54V and 25V supply)

    However the LED voltage on the board is fluctuating between 0 and 50 (can not make precise reading. Happens withing a second)

    Capacitors look fine

    Any ideas?
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    Tags: None
    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada
      #2
      Re: Philips 49PUT4900/12 no backlight

      Backlight issues are almost always the backlights themselves. Your LED tester puts out a lot less current than the power supply so may not catch the failure. You will need to open up the panel and test the strips or watch them flash. They may flash if the LED hasn't failed open circuit. The reason you can't measure any voltage is because the protection circuitry is kicking in and shutting down the backlights.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9625
          • Canada
          #3
          Re: Philips 49PUT4900/12 no backlight

          The power supply is likely fine, it only takes one led in the string to short to cause the backlight circuit to go into protection.

            Comment

            • Repair_dane
              Member
              • May 2020
              • 42
              • Danmark
              #4
              Re: Philips 49PUT4900/12 no backlight

              The voltage was measured both with and without the LEDs connected and in both cases it was fluctuating.
              I will take out the LEDs later today and check the individually

                Comment

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