T400s backlight issue *PICS*

[kraskm]

Hey everyone,

I'm replacing a few T400s and T410s screens for work and I replaced one in a T400s yesterday. Used the original wiring bus and everything worked fine at first.

However, I had reason to suspect that another one of my replacement screens was defective (same model of screen as the first replacement) so I connected it with another wiring bus (same part number but this one had been slightly damaged by another tech). When I started the T400s with this screen, it powered up but there was no backlight. I figured whatever, I have a DOA screen. Part was a toshiba LT141DEQ8B00, so equivalent to a Samsung LTN141BT08.

So I hooked up the first replacement and put the laptop back together. Now the backlight on the first replacement screen doesn't work.

Did I fry the backlight circut on the mainboard? If so, is there a reliable source for replacement mainboards?


On a related note there are two t410s that another tech couldn't fix that are now my responsibility. These machines had the replacement screens connected with new incorrect wiring. They now won't even recognize internal displays but work fine on externals. Thoughts on this situation?


Thanks in advance for any help,
Matt

[richk]

It is easy to blow a fuse on the motherboard. It is best to assume it is a fuse because that is about the only thing that can be fixed, but Lenovo would tell you that even fuses cannot be replaced, so anything you do trashes the warranty. The earlier boards had a fuse right by the connector that could be removed and replaced with proper soldering equipment. I actually have a T410s board in stock (actually, in my hand) that I could look at (Intel graphics, i5 520) but I couldn't tell what or where the fuse was without removing the plastic sheets, but I just pulled back the plastic a little bit. Also, it is easier to figure out what fuse is the one, if it has blown. There wasn't one anywhere I could see. I did not want to remove the plastic because it often tears and I did not want to damage the cosmetics, because the board is a good one and they are VERY expensive. There is no way for me to really tell without examining the board(s). I just cannot give you more info without seeing it/them. Send me a pm if you want to discuss further

[kraskm]

Thanks, I'll take a look at these boards and let you know if I think it's worth working on.

Matt

[sjthinkpader]

Are these screens LED types or CCF types? When you change the screens, CCF inverters may have to change to LED drivers or vice versa.

[richk]

T400s and T410s are all LED backlight and even on a T400 where there are both types, you can unplug one screen assembly and plug in the other type and nothing changes in regards to software, drivers or anything else outsifde the screen assembly

[quocturtle]

I am currently using T400s

Can I upgrade the screen into Multi-touch ??? If yes, where can I purchase?

[sjthinkpader]

I am currently using T400s

Can I upgrade the screen into Multi-touch ??? If yes, where can I purchase?

Multi-touch in the Thinkpad X61 Tablet lingo is stylus plus resistive. In Apple lingo means you can use 2 fingers to zoom in and out, rotate etc. In any case, you will have to add a touch pad controller which is usually a USB device even if you manage to attach the touch pad to the screen.

[rogertian]

as Richk mentioned it's easy to "blow a fuse on the motherboard", espeically when you plug on new screen without power off computer or even with battery.

And below pictures for your to identify where is it and how to fix it.

This indeed fixed my problem. Remeber: To remove baterry when you plug on screen.

[rogertian]

you were able to replace screen, i think you also know how to disasambly T400S machine. If you don't, check in websites.

[haci_87]

Hi,

do that fuse have some part number ?
Or shall i just direct connect without fuse ?

i have a T410s with same problem, i havent located the fuse yet but it sounds like its the same problem.

thanks

[deck42]

Hi! Have you located the fuse on your T410S??

I have the same model and same problem, would be great to know where the fuse on the T410s is!!

Thanks a lot!

[deck42]

Hi! Im trying to locate the same fuse on a T410s, but not getting anywhere - perhaps someone has an idea? I am posting pics of the same corner of the motherboard, of both sides! It is the corner around the display cable port. I know the images are not perfect, Im gonna try to get better ones!

https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing
https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing

EDIT - BETTER IMAGES:

https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing
https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing
https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing

Image with suspected fuses: (NOT sure yet!!)

https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing

[RealBlackStuff]

Have you measured the upper one in the red circle with a multimeter?
My suspect would be the bigger one, left of the top-right hole.
Looks like it has a 7 printed on it.

[richk]

It would be easier if I could see the board, but if I were guessing, I would guess that the big one with the "7" is for DC-in. The DC-in board plugs in right under that corner.

[deck42]

Dear all! Thank you very much for your help, but unfortunately we are not there yet. I have now checked all two footed chips in that area, with the following result: the only chip that clearly does not show any connectivity is the one marked on the back! On the front the three marked chips show little connectivity or Im not very sure if any at all. (they behave strange, sometime they show connectivity, then again they dont, but not systematic behaviour) How I measured: I measured the resistance. Any resistance between the two feet of any two footed chip and resistance >= 0 means connectivity while if the measuring device doesnt show any result there is no connectivity.

(btw.: yes you are right richk, the "7" chip is for the board underneath and it is ok as well)

Here are the photos with the marked candidates:

https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing
https://docs.google.com/file/d/0B7AtyUZ ... sp=sharing

[richk]

The brown ones (first picture) are capacitors, and it sounds like they behave like capacitors. A capacitor will pass current with no resistance for a period of time then behave like an open circuit. (the period of time depends on the rating - mF) Capacitors are often in parallel with a resistor. The second picture looks like a diode to me.

[RealBlackStuff]

There seems to be a fuse on suspected3.jpg (second link).
The gold-sided chip left above the connector with the 8 or B on it looks very much like one.

[authello]

Has anyone gone any further with this?
If anyone is interested i have some information regarding the t410s backlight issue.

[jayton4]

Always interested in new information!

[authello]

Well, the issue is definitely a fuse.
The fuse is rated at exactly the current draw of the backlight, the line for power to the backlight is always on this means that if you plug in or unplug an Lcd panel the spike in current blows the fuse. This will happen even if the laptop is turned off, as long as the battery or power adapter is supplying power to the mainboard.

It's easy to fix if you are confident with smd soldering.

Details to follow.

[billyboi02]

I have a T410s. I cannot locate the fuse. authello please post a pic of the location of the fuse.

[authello]

I am aware that i am taking some time to reply, guide will be made in two days, for now i will borrow another image from this thread and mark the fuse.

[authello]

https://docs.google.com/file/d/0B9qr2DV ... =drive_web
faulty part shown in blue.
This was doubly confirmed when the replacement mainboard sent directly from lenovo was reconditioned and a different fuse was fitted.

[authello]

Bugger, I'm new to this style of forum, can someone tell me how to image link correctly?

[RealBlackStuff]

You need to upload it to places like Google's Picasa, Imageshack, etc.
Once uploaded, that website will give you a link that you copy/paste here.

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People can look at that picture by clicking on the link.

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then click on the Img button at the top of this message.
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[_ub_]

Thank you, @rogertian for sharing your photos of the faulty fuse on the T400s mainboard.

http://www.51nb.com/forum/attachments/m ... xewlAt.jpg

This indeed fixed my problem, too! I had also plugged in the replacement panel while the main battery was still attached, and blown the fuse.

Mind though: This fuse on my board looked absolutely normal, even looking at it with 4x magnification. So without your photo, I would never have found the root cause of the dead backlight.

To test it, I powered up the mainboard and shorted the fuse, which lighted up the panel's backlight. Heureka!

So thanks again @rogertian for posting your insights and photo! It helped me repair my laptop with just a little effort excavating the mainboard's underside, and shunting the fuse.

BTW, to the previous post about fuses on T410s mainboards: The "missing" image link is this one: https://docs.google.com/file/d/0B9qr2DV ... V2QW8/edit I pulled this URL from the forum's source code. This T410s board looks quite different from my T400s board, but seeing the fuses there made me suspect that 'my' fuse might be broken without visible signs of damage.

[borisov87]

Thank you, @rogertian for sharing your photos of the faulty fuse on the T400s mainboard.

http://www.51nb.com/forum/attachments/m ... xewlAt.jpg

Please add new image, i have same problem. Connect new display to my 400s without power off, and display is now dimmed.
This is image of elements near my lcd connector.
https://drive.google.com/open?id=0BxqSF ... Vc5RHJBaFk

[RealBlackStuff]

From your picture, it looks like the fuse sits almost straight above the J5 marking, horizontal above the connector, in the middle between/under the 2 black chips, and looks like it has the letter F, which would be a .500A SMD fuse.

[SaskFellow]

Why would you do any internal work on any system with any form of power applied? That's just begging for stuff to get fried.



The important lesson here...

Disconnect the power supply and remove the battery before removing any screws.


Edit:

Not trying to be a dink, just trying to save you and anyone else who reads this some trouble. I almost ruined my T420s's motherboard because the fuse popped, and trying to get it replaced.

[marticka]

as Richk mentioned it's easy to "blow a fuse on the motherboard", espeically when you plug on new screen without power off computer or even with battery.

And below pictures for your to identify where is it and how to fix it.

This indeed fixed my problem. Remeber: To remove baterry when you plug on screen.

@rogertian Could you please post the pictures again? I am desperate in finding the fuses on my t400s to fix the problem with my backlight.

Until now I have found these two places with an "F" letter.
One is next to the display connector (1), the other next to the power chord input (2):

1)
(I WAS JUMPING THIS ONE BUT IT HAD NO EFFECT)

2)
(This one produce some sparks when I tried to jump it, but maybe I was not careful enough and touch sth. else, too)

Both of them from bigger distance, to understand their location: