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Lenovo ideapad L340-15API is no backlight

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    #1

    Lenovo ideapad L340-15API is no backlight

    Hi I have a problem with my Lenovo ideapad L340-15API there is no backlight and the LCD seems not to show anything, but I tested the laptop with an external monitor it works. I have tried to flash a new bios but it did not work. I tested the LCD power circuit and backlight power circuit I am getting the right voltages for both. I tested my screen and cable on another laptop and it works fine. So I don't know what to do now I am now suspecting the CPU, should I reflow the CPU?????
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    #2
    Re: Lenovo L340-171RH no backlight

    Originally posted by Nyashman View Post
    Hi I have a problem with my Lenovo ideapad L340-15API there is no backlight and the LCD seems not to show anything, but I tested the laptop with an external monitor it works. I have tried to flash a new bios but it did not work. I tested the LCD power circuit and backlight power circuit I am getting the right voltages for both. I tested my screen and cable on another laptop and it works fine. So I don't know what to do now I am now suspecting the CPU, should I reflow the CPU?????
    What voltage you get JEDP1 pin1 21 23

    Comment

      #3
      Re: Lenovo L340-171RH no backlight

      Pin 1= 11.23V on battery 19.56V on charger

      Pin 21= 3.33V

      Pin 23= 3.33V
      That is what I'm getting

      Comment

        #4
        Re: Lenovo L340-171RH no backlight

        Originally posted by Nyashman View Post
        Pin 1= 11.23V on battery 19.56V on charger

        Pin 21= 3.33V

        Pin 23= 3.33V
        That is what I'm getting
        If you have the schematic uploaded it in schematic section & for data & clock dispoff ?
        Last edited by Techtiger; 08-19-2023, 01:49 PM.

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          #5
          Re: Lenovo L340-171RH no backlight

          [QUOTE=techtiger;1263573]If you have the schematic uploaded it in schematic section & for data & clock dispoff ?

          I uploaded the schematic look at page 17

          MOD Edit: Link to schematic https://www.badcaps.net/forum/showthread.php?t=102633
          Reminder ,rules and organization of this section https://www.badcaps.net/forum/showthread.php?t=117483
          .
          Last edited by SMDFlea; 08-19-2023, 02:03 PM.

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            #6
            Re: Lenovo L340-171RH no backlight

            For dispoff I have 0V
            dmic data = 3.22V

            Comment

              #7
              Re: Lenovo L340-171RH no backlight

              Merci voltage on SIO pin 119? 109?

              Comment

                #8
                Re: Lenovo L340-171RH no backlight

                Sorry what do you mean

                OK I get it let me check

                119= 0

                109= 3.31v



                [Mod. Edit-Vesko356] Use if you want to add something instead of posting a new reply!
                Last edited by Vesko356; 08-19-2023, 02:55 PM. Reason: 3 posts merged.

                Comment

                  #9
                  Re: Lenovo L340-171RH no backlight

                  Voltage on U14 all pins ?

                  Comment

                    #10
                    Re: Lenovo L340-171RH no backlight

                    there is 3.32V on both the bottom pins and 0V on the top pin which is ground


                    Edit

                    I fixed it the cpu just needed a reflow and it worked.
                    Thank you techtiger for the support

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