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sajith
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Posts: 7
Registered: ‎05-10-2012
Location: US
Views: 33,003
Message 1 of 6

No screen backlight on T420

First it was cracks on the lid, then there was a stuck battery latch, then it stopped booting, and now there is no screen backlight. Oh Lenovo, what have you been doing to the beloved Thinkpad brand? :-(

 

It works with an external display, but that is not really the point of a laptop computer.

 

I have seen this thread ("T420 no backlight bad fuse?") here and this thread ("T420s with broken backlight - replace the whole panel?") in thinkpad.com forums and I am somewhat confused as on how to proceed from here.  I would like to avoid an expensive repair if this is something I could fix myself.  I am not entirely sure it is a blown fuse issue, because the no backlight problem occured a few times (it would not work sometimes on boot, sometimes it would) before it the backlight stopped working entirely.  It possibly is a loose contact somewhere.  Hopefully.  I suppose the hardware manual could help, but I am not sure what is it that I should look for.

 

Would you folks have any advice for me?

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Posts: 7,086
Registered: ‎01-13-2008
Location: US
Views: 32,515
Message 2 of 6
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Re: No screen backlight on T420

Community SeniorMod
Community SeniorMod
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Registered: ‎01-01-2010
Location: US
Views: 32,494
Message 3 of 6

Re: No screen backlight on T420

There is also a switch that senses that the lid is closed. I have seen one fail. On that machine, I could unplug the cable on the left side that has the connectors that control the LEDs on the control board.  The backlight would magically light.


Rich


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
vivien
What's DOS?
Posts: 2
Registered: ‎06-26-2013
Location: oxford uk
Views: 32,476
Message 4 of 6

Re: No screen backlight on T420

On my machine it turned out that the problem was being caused by the graphics driver. We uninstalled and reinstalled a newer one and it now works fine.

There were a couple of expert opinions;

1. it's your inverter (hardware problem)-based on the fact that the screen brightness faded suddenly (but didin't disappear) and that the screen was not bright on a reboot from before the login screen

2. It's a software problem- for which the solution was back everything up and do a reinstall

 

Was very glad that the guy who had seen exactly this problem before spotted it before either solution a or solution b happened.

dyziomax
Paper Tape
Posts: 3
Registered: ‎12-30-2015
Location: Poland
Views: 24,181
Message 5 of 6

Re: No screen backlight on T420

Hello,

vivien did You have backlight in bios ?
I have no backlight in bios and in Windows.
gege2
What's DOS?
Posts: 1
Registered: ‎06-05-2018
Location: PH
Views: 5,566
Message 6 of 6

Re: No screen backlight on T420

Hello I have lenovo thinkpad same problem backlight not function

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