Strange Thinkpad backlight issue

[LardChiviste]

Hi everyone ! For my first post here, I offer you some haunted Thinkpad stuff.

 

While visiting a friend recently, I came by a very strange issue affecting the backlight of his T440s' screen :

 

• When the computer is shutting down, as soon as the display turns off, the backlight will flicker with almost the same behavior as a good old disk activity LED.
• When the computer is OFF, some off the LEDs from the backlight strip will stay ON (and by off I mean whatever state UEFI computers enter nowadays when clicking shut down in the Windows start menu) and those LEDs are always the same.
• This happens when the computer is plugged to the wall adapter as well as just sitting on battery (if I remember correctly, the internal battery is not present in this one). When the external battery is removed, the LEDs turn off.
• When the computer is ON, everything looks fine, there's no flickering of any sort, the screen brightness doesn't seem to have changed since the problem appeared and brightness control still functions as it should.

 

My concern is that it could damage the battery by keeping it fully discharged too long if stored for some time (he uses this computer occasionnally for performing live music events, and there haven't been many since Covid hit).

 

So what is actually happening here ? I've heard of completely dead blacklights on various TXXXs models, but I haven't found any report of indvidual LEDs staying on while the computer is turned off. The pattern on the display reminds me of the stagelight issue affecting the 13" 2016 MacBook Pros, but that was a worn flat flex and happened only when the computer was actually on.

 

If that helps, this particular T440s is running Windows 10 pro off a 500GB SSHD, using only the 4GB of onboard RAM and powered by an i5 4300u. I think the screen is the base HD+ panel and not the higher end FHD option.

 

Of course you could suggest replacing the LCD panel (if it's indeed a LED strip issue) or the logic board (if it's an inverter issue for example), but where's the fun in that ? 

 

So if anyone has any experience with a similar issue or has any idea of what's going on here, I'm prepared to go down the rabbit hole !

[Radium_Angel]

27 minutes ago, LardChiviste said:

live music events

 

27 minutes ago, LardChiviste said:

stagelight issue

I think the problem is pretty obvious, don't you? The laptop is missing the rave parties it used to go to, and it's trying to relive those fond memories. 

 

On a more serious note:

My first thought is the inverter board, but that typically shows signs of failing when the system is on, not off. 

My next thought is power leakage somewhere, the screen is getting power still even when the system is off, but even if that were the case, I"d have no idea how to fix, since laptops aren't generally made to be user-serviceable

 

If he doesn't use the laptop that often, I'd suggest removing the batteries when not in use.