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rant-ninja
6y

Seeking help from anyone able to read Laptop motherboard semantics sheet

In short: Looking for a blown fuse on Laptop (Dell Inspiron 7547) near LCD cable connector, as not getting backlight after a new screen installation. Screen is functional and is detected properly and the device is passing all the diagnostics tests.

Issue tracked here
https://reddit.com/r/Dell/...
And here,
http://tomsguide.com/answers/...

Thanks ++

question

diy

no backlight

laptop

repair

blown fuse

led

dim display

semantics
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  • 1
    6y
    Update:

    https://dropbox.com/s/...

    Basing on this:

    From to page 31, i'm going to check voltage value for R420 or Q25 and see where we go from there.

    Why? Documenting coz someone with a random google search may come up here and can solve the issue. :)
  • 0
    6y
    @rant-ninja https://imgur.com/a/JNpPec9
  • 1
    6y
    SOLVED.

    A bit of multi-meter readings found out that Q25 is faulty as a reason Q22 is not able to current it needs to power on the backlight.

    So for now I've shorted R420 as a temporary fix to bypass that.

    They both are near 40pin LCD connector on board.

    Anyone referring the post check P31 of board schematics here.(https://dropbox.com/s/...)
  • 0
    6y
    Refer above.
  • 1
    6y
    Everything here:

    https://imgur.com/a/JNpPec9
  • 1
    5y
    @rant-ninja

    Thank you so much for your very detailed report!

    I was facing the same issue, except for my Dell Inspiron 7559, The schematics are found here: https://tinyurl.com/y8sltxen

    Just like you, a mosfet was the problem. For me, it was Q7 for my laptop schematics. Replacing the mosfet fixed the backlight issue - the job took some tricky soldering and a 50 cents part.
  • 0
    5y
    @Merudo Good work. Glad it was of some help. I just checked the site after ages (had built up rants for a while now).
  • 0
    3y
    @rant-ninja Hello.
    I have the exact same problem with my Inspiron 7547 but I'm not very good with electronics.
    I'm contemplating applying your fix, but can you tell me the risks of shorting those paths across the MOSFET? Thanks in advance
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