Lenovo U330P backlight problem

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  • Dr.xyz
    Member
    • Jan 2018
    • 11
    • Finland
    #1

    Lenovo U330P backlight problem

    Hi,

    Mobo Quanta LZ5. Screen backlight stays on at bios, but when booting to any operating system, when panel switches to higher resolution, backlight turns off.

    Still can see picture with flashlight and everything else works normally. Backlight voltage from mobo seems low, only ~8 volts. Is this correct?

    Laptop was worked on by another shop, they tested display panel in another computer and it was OK, so issue is with motherboard.

    Schematics from backlight voltage producing area would be nice...
    Tags: None
    • piernov
      Super Moderator
      • Jan 2016
      • 4439
      • France
      #2
      Re: Lenovo U330P backlight problem

      Sounds like a driver issue. Did you try on a Linux LiveUSB operating system?
      OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

        Comment

        • Dr.xyz
          Member
          • Jan 2018
          • 11
          • Finland
          #3
          Re: Lenovo U330P backlight problem

          Yes, tried live linux. Backlight turns off soon after booting when resolution changes. Not a driver issue.

            Comment

            • Dr.xyz
              Member
              • Jan 2018
              • 11
              • Finland
              #4
              Re: Lenovo U330P backlight problem

              Lid switch is OK.

              When changing resolution from OS desktop, backlight briefly flashes once, but never stays on.

                Comment

                • SMDFlea
                  Super Moderator
                  • Jan 2018
                  • 21849
                  • UK
                  #5
                  Re: Lenovo U330P backlight problem

                  Theres a schematic here on the other U330 thread https://www.badcaps.net/forum/showthread.php?t=70371
                  All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

                    Comment

                    • Dr.xyz
                      Member
                      • Jan 2018
                      • 11
                      • Finland
                      #6
                      Re: Lenovo U330P backlight problem

                      Yes, already have it.

                      Removed Q1, no change. At least LCD_BK_OFF signal is not the cause. Will continue tomorrow with remaining PANEL_BKEN and DISPON signals.

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