ThinkPad T400 LCD not illuminated (no backlight) *PICS*

[ReCreate]

This was very helpful for me, Thanks. I have the same issue with my T400, and I wrote a small article describing my solution in my blog, and I linked to your post as a credit.

http://housecat.name/?p=34

It can happen easily if you disconnect the LCD while power is on. The manual says to not do that for a reason!

[nadia]

Hello guys, I had the same problem with my ThinkPad T400. Thanks to your photos and your explanations I've solved the problem. Now it works fine. You were really valuable.

[NOSIRROM]

Check the power wires coming from the back of the internal dc jack and the mother board look where it goes under the hinges that hold the screen had one that got pinched their and matches all you issues

[smalltobi]

Hi!

I think I have the same problem with my Thinkpad T400. I took a picture of the fuse locations. It does not look exactly the same as the one posted here... do you think these are the right fuses? I want to be really sure about that, before I start fixing the hardware...

https://www.anony.ws/i/2016/02/26/think ... ations.png

[rmdferreira]

Had the same problem and it's solved now. I found the solution somewhere else and I couldn't locate the same now, so I'll add my screenshots and case now
In this case, the lcd backlight and indicator lights are not working, except the wifi led (leftmost the indicator lights row), if you connect your laptop to an external monitor you'll have an output.
The problem here is that no power is reaching the display section, usually for one of two reasons:
* Either the LCD cable is damaged (the power line(s) of the cable connecting the mobo to the LCD are cut), this case you'll need to replace the cable (my LCD cable model is 93P4593, it's similar to the one in http://goo.gl/iQ9Ze9).
* Or it's just a fuse that needs to be replaced or jumped, this was the problem of my T400. Here's what I did:
1) Remove the palmrest and keyboard
2) locate the display cable connection to the motherboard (mobo), you'll need to remove one screw which fixes the cable to the mobo.
3) locate the two fuses, marked in red ellipses in the following image. The fuses are very tiny, their lengths are around 1.5ml and 0.5ml, found just under the aluminium chassis/frame. The photo is taken from above the screen which was laid back 180 degrees.
http://i90.photobucket.com/albums/k274/ ... ac045c.jpg
4) Replace (safer, but needs an expert service) or jump (as a last solution) the fuses. I jumped them using a "conductive wire glue", like the one found in http://goo.gl/VFQBsz. The fuses are not so easy to access, I used the needle provided with the conductive wire glue syringe. Here's the result:
http://i90.photobucket.com/albums/k274/ ... e33b8c.jpg
5) Assembled everything, waited 8 hours to make sure the glue dried, switched on my laptop and the LCD and leds were totally working.
Hope this helps somebody out there.

Do you know where can i find these two fuses? is there any serial number? Reference?

tks
Ricardo

[theterminator93]

Ancient topic, but I'll add the info below in response to the above.

I had to replace the LCD fuses on my W520 (twice!!) during my IPS screen fitments... it's doable without all the fancy electronics shop equipment but it requires patience, care, and a steady hand. The fuses I bought were Littelfuse branded - the backlight fuse was an SMD 0603 size, 3A and 32V. The electronics fuse was SMD 0603 as well, but .5A at 32V. May be slightly different on the T4/500, but would probably be a good starting point.

[deickos]

I have read the current thread here and another with the same theme in lenovo forums and indeed the culprit is the blown fuses as richk says. What is not mentioned though in both places is HOW and WHY these fuses are blown.
As I learnt from an exceptional technician from England this happens from defective lcd cable - and thus will happen again after the mb is replaced or repaired. So it is important to rid of the cable and get a new one.