T440 Built-In Display, Trackpad, & Keyboard Not Working.

[GeorgeM]

Hello!

I have a T440 (not the T440P or T440S) with an i5 and 8Gb of RAM but the display, trackpad, & keyboard aren't working. I've had the device for over a year and the only problem with it was that the reset button on the underside would occasionally need to be pressed after hot-swapping the removable battery in order for the device to boot up again.

This didn't bother me much until it happened one day and I had nothing small enough to be able to reach the reset button since I was at college. As soon as I got home, I managed to press it but things didn't return to normal. The device wouldn't boot up at all and showed little to no signs of life. Eventually I fixed most of the issues - including one or two from the RTC battery - and was able to use the device when plugged into an external monitor, keyboard, & mouse.

It's been like this for quite a few months now and I really need it fixed for my studies. I have already asked on the Lenovo community forum a while ago but I didn't get any support regarding this exact issue. Since then, I've been trying desperately to get it fully working again but with no luck. Any help would be hugely appreciated. Stay safe.

[RealBlackStuff]

Get the T440 manual from the HMM link at the top of this page.
Remove power and both batteries before you open it up!
Check that all (flat)cables are properly connected.
Did you previously take that machine apart or disconnected the LCD while the internal battery was still connected?
In that case you may have blown the backlight fuse.
If the RTC battery causes problems, usually it needs to be replaced and the date/time reset.
Make sure you know any passwords in the BIOS before you do the swap!

[GeorgeM]

Firstly, thank you for your fast reply.
I've downloaded the T440 manual for future reference now.
I can confirm, after checking dozens of times, that all the cables are properly connected.
I have previously taken the machine apart once or twice and, although I'd like to think I didn't make the mistake of disconnecting the LCD whilst the internal battery was still connected, there is a strong possibility that this is the case.
What options are there for replacing the backlight fuse? (Is that found on the device's motherboard or the circuitry on the LCD itself?)
I've tested the voltage of the RTC battery and it's perfectly fine so that shouldn't need replacing.

[RealBlackStuff]

Check Fuse F3 (3A, 32V, Fast, Type=ERBRD3R00X) near the LCD-connector on the motherboard.
It is tiny size 0402.
Available e.g. here: https://www.amazon.co.uk/ERBRD3R00X-Qui ... B0137JFAN2
You could also try and piggy-back solder the slightly larger size 0603 (Type=0467003.NRHF) on top of the old one.
Available e.g. here: https://uk.farnell.com/littelfuse/04670 ... dp/2786401

Remove the trackpad cable and see if the KB then works.