Take a look at our
ThinkPads.com HOME PAGE
For those who might want to contribute to the blog, start here: Editors Alley Topic
Then contact Bill with a Private Message

T440p FHD IPS screen back light gone

T430 and later, plus T530 and later series specific matters only
Post Reply
Message
Author
Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

T440p FHD IPS screen back light gone

#1 Post by Natakranta » Thu Apr 09, 2020 11:37 am

Hi Guys,
I have T440p which I bought few months ago with good working FHD IPS screen, good find I couldn't resist :) Laptop screen was good and I was happy to score a FHD IPS to save me this upgrade.
Laptop was siting with lid closed on docking station with external monitor connected and used daily. One day I opened it and noticed laptop screen is no longer working. It was dead black, or I thought so. I got a hint to light a flashlight on it and to my surprise I noticed the picture is there, just so dim almost invisible. Conclusion: Screen back light is gone. I purchased new screen which has just arrived. 2 minute job to put it on and... it is not working. I see the same when looking at it in a daylight or with flashlight, picture is there if I look close from few centimeters.
I'd say it's unlikely I got a screen with broken back light. My next thought is that maybe the cable is broken, or at least the line responsible for providing power to back light leds. What do you think?
I have a 30pin cable left from my T540p when I was doing upgrade to QHD screen and had to replace it with 40pin cable. Do you know if it would fit T440p. Screen connector is exactly the same 30 pin, it fits the screen. Not sure about motherboard connector and length of the cable, should be long enough I guess. What do you think?
I need to watch some disassembly videos to see how to get to the connector on motherboard.

RealBlackStuff
Admin Emeritus
Admin Emeritus
Posts: 21264
Joined: Mon Sep 18, 2006 5:17 am
Location: Dublin, Éire
Contact:

Re: T440p FHD IPS screen back light gone

#2 Post by RealBlackStuff » Thu Apr 09, 2020 11:47 am

More likely it is a blown fuse F3 (3A/32V/fast, marked with a P) near the LCD-connector on the motherboard.
Measure it for Continuity with a multimeter.
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!
Check out The Boardroom for Parts, Mods and Other Services.
Covid-19: Mask it or casket.

Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

Re: T440p FHD IPS screen back light gone

#3 Post by Natakranta » Thu Apr 09, 2020 12:03 pm

Is it common for these fuses to blow without a reason? I mean I don't recall doing anything that could blow it? I read that they can blow if you don't disconnect battery when replacing the screen, but it's not the case here. Laptop was just siting on docking station with lid closed and screen off when it supposedly happened some day.
Any good disassembly video how to get to the motherboard on T440p? What I found on YouTube so far is only CPU, RAM, drives, keyboard and clunkpad replacing videos.
I have an electronic multimeter but I am not electrician, not sure what settings set on it A,V, Ohms, this is voodoo to me, I do Credits and Debits professionally :D

Update:
I looked through HMM and this YouTube video of T440p disassembly. Screen cable connector is on left side of the keyboard. Taking off the palm rest gives access to it. What I can't see is if it is enough to access the back light fuse to test it. I think the fuse is under the metal frame and I'll need to completely remove the motherboard to bet access to this fuse. Please correct me if I'm (hopefully) wrong.

Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

Re: T440p FHD IPS screen back light gone

#4 Post by Natakranta » Thu Apr 16, 2020 2:42 pm

I took off palmrest in search of display cable connector on motherboard.
picture of the port, unfortunately no access to the back light fuses :( I'm guessing they must be on the right side of the port under the metal frame. I'm not disassembling it further as I don't have soldering gun, I have zero soldering experience, and I don't have any replacement fuses. I need to wait for the end of lockdown and take it to nearest board repair shop to replace the fuse, assuming it is the burned fuse causing the lack of back light.


I have a spare T540p FHD 30 pin cable which has then same display connector as T440p cable, but as you can see longer connector on the motherboard side. So if it's cable (and not fuse, unlikely) there goes my free replacement not fitting.

RealBlackStuff
Admin Emeritus
Admin Emeritus
Posts: 21264
Joined: Mon Sep 18, 2006 5:17 am
Location: Dublin, Éire
Contact:

Re: T440p FHD IPS screen back light gone

#5 Post by RealBlackStuff » Fri Apr 17, 2020 3:06 am

The fuse F3 is under the chassis, on your picture above the connector and directly above the letter J (JEDP1).
It means you'll have to take the motherboard out.
Here's a more detailed picture: https://i.imgur.com/9F6hJbw.jpg

The original fuse F3 is: 3A, 32V, Fast, ERBRD3R00X, size is a tiny 0402
You can order them from RS/Radionics in Dolphin's Barn/D12:
But since there is ample space on the motherboard, it would be easier to remove the old fuse and replace it with a larger size 1206
0402 ERBRD3R00X: https://ie.rs-online.com/web/p/non-rese ... s/7594763/
1206 0466003.NR : https://ie.rs-online.com/web/p/non-rese ... s/5413619/
If you are not up for that, you know where to find me.
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!
Check out The Boardroom for Parts, Mods and Other Services.
Covid-19: Mask it or casket.

Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

Re: T440p FHD IPS screen back light gone

#6 Post by Natakranta » Sun Apr 19, 2020 6:39 pm

Thanks a mill @RealBlackStuff for your detailed answer. So much appreciated, but I don't have soldering hot air gun nor the skills to proceed. First I'll check if I can get it sorted in some local repair shop nearby to save me on postage both ways. If no luck or some ridiculous pricing, I'll get back to you. Thanks!

Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

Re: T440p FHD IPS screen back light gone

#7 Post by Natakranta » Tue Jul 14, 2020 5:19 pm

Waiting on my exams results (tomorrow, fingers crossed) I had time to disassemble my T440p with missing backlight.
Local guy I bough T480 :) from had repair shop with soldering station under microscope. He checked the F3 fuse and said it was fine, no problem with it. Looking around he found the fuse just above F7 was blown. He didn't have replacement fuse so with my OK he bridged it with micro wire.
picture, blown and bridged fuse marked with red arrow.
I have just put it all together and no luck :( screen still not showing picture.
I'll put it on docking station tomorrow to see if it works at all. It was working fine on docking station with external monitor even with its own screen not working.

RealBlackStuff
Admin Emeritus
Admin Emeritus
Posts: 21264
Joined: Mon Sep 18, 2006 5:17 am
Location: Dublin, Éire
Contact:

Re: T440p FHD IPS screen back light gone

#8 Post by RealBlackStuff » Wed Jul 15, 2020 4:14 am

F3 and F7 are identical fuses (ERBRD3R00X = 3A/32V/fast, size 0402).
From your picture, if the F7 text is printed/placed correctly, it looks like that shop-guy bridged the capacitor (or resistor) next to it, instead of the F7 fuse...
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!
Check out The Boardroom for Parts, Mods and Other Services.
Covid-19: Mask it or casket.

Natakranta
Freshman Member
Posts: 65
Joined: Mon Dec 30, 2019 3:48 am
Location: Dublin, Ireland

Re: T440p FHD IPS screen back light gone

#9 Post by Natakranta » Wed Jul 15, 2020 10:48 am

Well, I'm not electrician :mrgreen: he checked F3 as I asked him and said it is not blown, but working just fine.
Then he started checking others and said that one is broken and bridged it. Could not be that measuring capacitor shows a result of blown fuse, like if you think you are measuring a fuse and don't suspect it's actually a capacitor?
(I see you smiling, but I only now googled what's the difference between one and the other :D )

Anyway, he neither fixed it nor broke it. I put assembled laptop on docking station, reset time and date in BIOS and installed W10 on m.2 SSD (in WWAN slot, no main drive for the moment). Well, at least I didn't break anything neither disassembling and reassembling it. Only laptops' screen is still missing backlight (I can see text if I direct flashlight directly on it)

Post Reply
  • Similar Topics
    Replies
    Views
    Last post

Return to “ThinkPad T430-T490 / T530-T590 Series”

Who is online

Users browsing this forum: No registered users and 12 guests