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Laptop screen issue

GiGaCCM Posted messages 4 Registration date   Status Member Last intervention   -  
Didi64_549 Posted messages 2866 Registration date   Status Member Last intervention   -

Hello,

I accidentally broke my laptop screen. Only half of it works. So I ordered a new screen. Note that I detached the broken screen without being able to power off the laptop. After replacing the screen, there is no display on the new one. I then reassembled the defective screen, and still no display, even though before disassembly one half was still working.
Could the graphics card have been damaged?
I connected a video projector to guide myself, and it works; I do have a projection on the screen. So is the graphics card linked to HDMI?
I had disassembled and reassembled the screen taking great care with the connector.

Would anyone have any idea? Replacing the cable, which could have been damaged anyway? ?

Lenovo L340API17 laptop
Windows 11

2 answers

  1.
    Didi64_549 Posted messages 2866 Registration date   Status Member Last intervention  
     

    Hello,

    If the graphics card were at fault because the HDMI wouldn’t work either.

    Perhaps a defective ribbon cable after the delivery?

    Also check the motherboard connector.

    On Lenovos I noticed there is a small fuse marked with a letter F or FL that protects the backlight power line, and if that one is blown it’s black even if the panel is fine.

    The disassembly either pulled the ribbon too hard and damaged a trace, but the fuse should be checked to see if it’s good.

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    1. GiGaCCM Posted messages 4 Registration date   Status Member Last intervention  
       

      Hello,

      Thank you for the information. I will check if I can see a fuse. On the motherboard side, I haven't touched anything; I only removed the frame of the screen and detached the connector on it.

      The ribbon cable wasn't sold with the screen; I just unplugged the connector.

      Regarding the graphics card information about HDMI. It seemed logical to me, but I wasn't sure. Thanks for confirming.

      I will test and get back to you.

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      1. GiGaCCM Posted messages 4 Registration date   Status Member Last intervention   > GiGaCCM Posted messages 4 Registration date   Status Member Last intervention  
         

        Well, I’ve reassembled the new panel, and by shining a flashlight (electric) on the screen, I can glimpse the display. So it’s definitely a backlight issue.

        Now to find the fuse reference. There are three near the connector on the board (F3, F4 and F11), but none of them affect the backlight.

        If it’s on the back of the board, I’ll have to dismantle everything...

        Or Lenovo support?

        Any suggestions?

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      2. Didi64_549 Posted messages 2866 Registration date   Status Member Last intervention   > GiGaCCM Posted messages 4 Registration date   Status Member Last intervention  
         
        Re, These fuses F3, F4 or F11 power the backlight supply and the LCD controller supply. Test with another eDP cable, because even though it doesn’t appear damaged, it may be. One of the cables or the cable itself may be torn or even cut inside its sheath. Don’t you have someone nearby who can lend you a multimeter to test the fuses as well? If you know how to do it, replace all three fuses and then see the result.
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      3. GiGaCCM Posted messages 4 Registration date   Status Member Last intervention   > Didi64_549 Posted messages 2866 Registration date   Status Member Last intervention  
         

        Thank you Didi64_549,

        I checked with the multimeter, and indeed the fuses F4 and F11 are no longer conducting. As for replacement, it seems impossible for me :
        1- due to the size (less than 1 mm)
        2- due to their availability on the market.

        I could possibly re-solder them, but where to find them ... ?

        Maybe bypass them?

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  2. Didi64_549 Posted messages 2866 Registration date   Status Member Last intervention  
     

    Hi again,

    Try to see if you can enter the BIOS at startup of the PC by pressing F1 or F2 as soon as it begins to boot.

    If there is really no display even in the BIOS, it’s a hardware problem, hence the fuses or even the motherboard.

    You should check if you can find an identical used one to test, and you’ll see later what you decide before bypassing.

    Make sure the connector next to the motherboard is perfectly seated, especially if you need to recheck it and ensure there is no play.

    Afterwards you can clean the contacts with isopropyl alcohol as well.

    For me the ribbon cable remains the No. 1 suspect.

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