Lenovo nm-a161 no backlight

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  • f-bone
    Senior Member
    • May 2013
    • 96
    • Greece

    #1

    Lenovo nm-a161 no backlight

    Hi guys,

    I got this motherboard that has picture without backlight.

    I measured +LEDVDD at 19V and also other voltages are present at LVDS connector. LID_SW# is at 3.3V and I noticed that BKOFF# is always LOW (0V). I tried new clean ME bios as well.

    Any pointers are really appreciated.

    BR,
    George
    Attached Files
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14062
    • Canada

    #2
    Re: Lenovo nm-a161 no backlight

    Measure the voltage on LID_SW#, with the LID open. Then repeat with the LID closed.

    Any changes to the voltage values?

    The LID_SW# must be used by the IT8586E/AX (UE1) to then turn the backlight ON / OFF.

    Comment

    • mcplslg123
      Badcaps Legend
      • Jun 2015
      • 7262
      • india

      #3
      Re: Lenovo nm-a161 no backlight

      Ive faced BKOFF# being low on many Lenovo SOC mb's specially on LA-C771P(3-4 units so far). It was SOC fault in my case. I just cut the track of BKOFF# pin from EDP connector, removed the BKOFF# cable from EDP cable and connected it to 3v source from mb. It works now though brightness adjustment is no more available. Try it as a last resort but first findout the reason.

      Comment

      • f-bone
        Senior Member
        • May 2013
        • 96
        • Greece

        #4
        Re: Lenovo nm-a161 no backlight

        @mon2 I measured LID_SW# while the motherboard was on my bench with a LCD connected.. no BKLT.

        @mcplslg123 I tried that - I cut the trace going to pin 30 and attached a jumper wire to the LVDS connector directly and to LCDVDD_CON capacitor. No dice.. maybe I should try +3VS?

        Comment

        • mcplslg123
          Badcaps Legend
          • Jun 2015
          • 7262
          • india

          #5
          Re: Lenovo nm-a161 no backlight

          @f-bone, you are shorting LCD_VDD to BKOFF# thru that jumper. It wont work. Take +3VS from any other source and connect it to pin30. Hopefully will work. If you have dc supply, then u can inject 3v directly on pin30 and see if u get backlit.

          Comment

          • ktmmotocross
            Boardkiller
            • Feb 2014
            • 3581
            • slovakia

            #6
            Re: Lenovo nm-a161 no backlight

            # - means that signal is ACTIVE with LOW voltage

            Comment

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