Question about Lenovo ThinkPad T420 Notebook

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I have a lenovo t420 which has brightness/dim issue and can't correct it by unchecking the auto brightness

My Lenovo laptop has started to go from bright to dim on the display about every second .I tried to delete auto brightness on the intel hd graphics but to no avail. I am running windows 7 ultimate .really need help trying to fix this problem .

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There should be a function key to adjust the brightness at the top of your keyboard my laptop is F2 or F3 so at the bottom of the keyboard is a key label FN The Function key looks like a sun with an arrow if you are lucky to have it labelled.
If this does not fix problem you may have a faulty laptop . There is a circuit called an inverter in your laptop that converts DC to a higher voltage AC to run the fluro backlight behind your laptop's LCD screen. If this inverter goes faulty you could experience the symptoms you are seeing. This would require a replacement of the inverter circuit board in your laptop by a repair service centre.
http://www.youtube.com/watch?v=fSCJzA0EBo0
http://www.youtube.com/watch?v=2Yi6GNFcP3w
http://ask.metafilter.com/92210/Backlight-or-Inverter-How-can-you-tell

Posted on Sep 05, 2014

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  • Expert
  • 54 Answers

Try it with another monitor. Is the monitor dimming? or just only your TFT/LCD panel?

Posted on Sep 05, 2014

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6ya6ya

6ya staff

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Posted on Jan 02, 2017

bronk50

Brian Sullivan

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SOURCE: Intel graphics media driver update wiped out my

click start control panel administrive tools computer management device manager scoll to ports(com&lpt)right click to scan for hardware changes or scroll to monitors + to expand plug and play monitor right click where you have options to update driver,disable.uninstall,scan for hardware changes or select properties where in the general you have the option to troubleshoot also in the driver tab you have the same options as when you first right click on monitor also
click start control panel,display,desktop you can select a different desktop from the drop down list also settings you can change the settings for more or less pixels or from the drop down list pick the appropriate level of color range or troubleshoot also select advanced then general dpi normal size,larger size or custom settings
always click APPLY after making any changes
hope this helps

Posted on Feb 08, 2011

lauri68

lauri68

  • 2 Answers

SOURCE: Stuttering

I think it might be that your PC is too clogged up by various programmes and background runs. I would format and install. (How long have you been using it in years, months? How many different programs on it? How much RAM?)

Posted on Apr 30, 2012

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I have alenovo t420 laptop that brightens and dims every second or so . tried diablind the automactic brighten button under intel but this didn't work . am at a lost and need help .


Is it problem accours in another monitor that pluged to your notebook? If no, the possibility is inverter failure. Try to replace the inverter to your service centre

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How do i fix an issue wth the brightness on my lenovo t420 dimming every second


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Factory restore using command prompt


http://www.google.com.ua/search?q=Lenovo+THINKPAD+T420&oq=Lenovo+THINKPAD+T420&sugexp=chrome,mod=8&sourceid=chrome&ie=UTF-8#hl=ru&tbo=d&sclient=psy-ab&q=Lenovo+THINKPAD+T420+recovery&oq=Lenovo+THINKPAD+T420+recovery&gs_l=serp.3..0l2.1216.3253.0.3714.9.5.0.4.4.0.223.701.0j4j1.5.0...0.0...1c.1.14pecXA4UK8&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=30f8933bc1ffddc8&bpcl=38625945&biw=1366&bih=643

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I need a user manual for a Levono ThinkPad T420. Where can I download a free one?


For T420 model Lenovo doesn't call it "User Manual" instead calls it "Hardware Maintenance Manual".
Here's a link to that manual:
http://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/0a60007.pdf

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