Thinkpad L540 No backlight on LG or Samsung screen but works with AUO

Discussion in 'Hardware Components and Aftermarket Upgrades' started by mcfpet, Jul 23, 2020.

  1. mcfpet

    mcfpet Newbie

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    I too came to the conclusion that it was probably just bad soldering. I would be very grateful for preparing a mod based on original dump.
    Original L540 dump: https://www.sendspace.com/file/auv2gw
    SHA256: fe974d5241c510713a2968490e4f04af646d14a0260194861de155a5e7d4cd6c

    Modded version (with BIOS v1.11) : https://www.sendspace.com/file/cupxu2
    SHA256: ff1fbd1d20040c1fa2ae04b678f6cdefe167f2ed1ba3a1e70b614d7c97211fb0

    Edit:
    chips's still alive, I managed to read contents of the chip with broken pin (this cheap aliexpress SO-8 clip really came in handy) - and it matches the 'modded' file, so it's even more likely that sloppy soldering is to blame.
     
    Last edited: Aug 8, 2020
  2. t456

    t456 1977-09-05, 12:56:00 UTC Moderator

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    Sorry for the late reply; vacation.

    And ok, is it working now then? Backlight and all or still waiting for the replacement chip?

    If so then I'll hold off on the mod until it arrives. Suppose the v1.11 mod should suffice too.
     
  3. mcfpet

    mcfpet Newbie

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    It's ok. The "broken" chip kinda worked after flashing it with an old BIOS copy and soldering a cooper wire to the broken pin. By "working" I mean motherboard booting without backlight. It doesn't seem like a permanent solution though. Anyway, the replacement chip has just arrived, so I'm ready to flash it with modded v1.06.
     
  4. Tech Junky

    Tech Junky Notebook Consultant

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    One thing I noticed while looking at panels / replacements is AUO has a different pin pitch of 0.4mm vs other MFG's at 0.5mm on the panel connection side. There are a few AUO models that are more standard with 0.5mm connections though.

    Might be as simple as the eDP cable from the MOBO to the panel? Could also be a Voltage difference that the mobo can't supply enough juice to power the panels properly.
     
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