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[Pictures] Location of backlight fuse on T420

T400/410/420 and T500/510/520 series specific matters only
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TPFanatic
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[Pictures] Location of backlight fuse on T420

#1 Post by TPFanatic » Mon Dec 11, 2017 3:51 pm

Blew the backlight fuse on my T420
What fuse to buy?
And where on the board to piggy-back?

edit:

Found this post on tomsguide which detailed the fuse location:
hackoff wrote:i could wait for an answer till the end of the universe. so i took my multimeter a found all fuses near display connector and started with measuring resistance. there were fuses F2, F10 which had some mili Ohms resistance. so they were OK. after that i found one fuse on the reverse side of the board exactly on the place of the connector on the front side. my ohm meter said it has infinite resistance so it means that fuse is already broken. i think it was F7 fuse.
when i knew which fuse is broken i took solder and went to work. i didnt try to remove it because that board has more layers so i could demage connections if i would try to remove it. i just simply made a soldering bridge/short over that fuse.
i made a power on test and lcd backlight was shining like it was in the time of manufacturing.
i hope this helps a little for others with similar problem. but this solution is dangerous if you will once more make a mistake to work on display with power/battery on. next time you will propably demage something on motherboard.
As for images:
https://s33.postimg.org/no3atcphr/DSCN9703a.jpg
https://s33.postimg.org/p34vi2iv3/DSCN9704a.jpg
Last edited by TPFanatic on Sun Dec 17, 2017 11:05 am, edited 2 times in total.
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theterminator93
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Re: Location of backlight fuse on T420

#2 Post by theterminator93 » Mon Dec 11, 2017 5:02 pm

I blew the backlight fuse on my W520 more than once. In my case it was on the underside of the board under the black tape near the DIMM sockets and docking connector - the fuses will be labeled labeled Fxx (e.g. F6) so they should be relatively easy to find. Ohming out across them will help you confirm which is blown.

The fuse is an 0603 size, 3A; I bought "Littelfuse SMD 0603 Fast Acting Fuse 3A 32V" on eBay for my application, working marvelously.
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Re: [Pictures] Location of backlight fuse on T420

#3 Post by TPFanatic » Sun Dec 17, 2017 11:05 am

Fuse found OP updated with images.
lenovo X230 i5 3320m IPS 8GB
lenovo T430 i5 3320m FHD 8GB
lenovo T500 P9700 WUXGA 8GB


Enable 2 finger scroll on any Synaptics touchpads with registry: http://forum.thinkpads.com/viewtopic.php?f=2&t=122612

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