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  • Message 11 of 15

Re: Lenovo T400 very dark screen

2014-07-17, 5:39 AM


When I start the laptop I can see very hardly (in very darkness) the starting page, and after that almoast nothing.

Even after replacing the whole LCD assembly (LCD + inverter + LCD cable), it stays the same.

I'm asking about the fuse in the motherboard, because when I had similar problem with the T400s very dark screen (but the one is the LED panel without the inverter) there's the fuse burned in the motherboard.



actually a screen which is ALMOST dark (very dim image still visible) CAN be caused by a blown (as you call it "burned") fuse in the system board. Since you say you have tried swapping over an ENTIRE LCD assembly (LCD+inverter+LCD cable) then the only possibility left IS a blown fuse/ fuses on the system board (motherboard). One important question: Was the ENTIRE LCD assembly (which you swapped over onto THIS board) known to be working for certain? Did you test it again in ANOTHER machine AFTER trying it on THIS board? If so, then unfortunately the problem must be blown fuse/ fuses on THIS board. Replacing fuses would require a very precise (fine tip) soldering iron and steady hands. And you would have to test and locate the correct fuses. It is a job for a highly skilled technician, not an easy DIY (Do It Yourself) project for the average person. So most people will just replace the entire system board in such a case. But if the machine will still display to an external monitor then you could still use it that way, if that is acceptable for you.


But there is one last thing you can try since you have nothing to lose. But don't get your hopes up :smileysad: This is  NOT LIKELY to solve YOUR problem, because of the pattern you are describing. Usually "CMOS corruption" or "CMOS reset trick" is successful with these symptoms mentioned by another forum member: "The laptop powered on with a flicker in the display. Then I could only see backlight in the display. In the light panel only the plug sign and the z sign was lit. no activity in the HDD light even though I could hear the HDD spinning... I have tried a secondary monitor. No response." So this procedure is likely to work when there is NO image/ text which can be seen (only a faint light on the display), and there was no warning, no symptoms of failing screen, although the display worked fine the previous day. T400 especially seems to suffer a lot more than other models from this "CMOS corruption"- but a few people have reported R400 too, which makes sense, since it has almost exact same hardware as T400. I have personally used this "CMOS reset trick" on a non-posting T400 I bought at a VERY low price.  I took a gamble, after reading the lack of display/ symptoms the seller was describing- and guess what? It worked! And no problems with that T400 to this day. Here is the forum member it just worked for, whom I quoted above, but like I said, this method will PROBABLY NOT WORK IN YOUR CASE: http://forums.lenovo.com/t5/T400-T500-and-newer-T-series/No-Display/m-p/1617628#M99350

Have a great day. (I do not work for Lenovo)

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  • Message 12 of 15

Re: Lenovo T400 very dark screen

2014-07-17, 6:15 AM

So the way described by Anastasios make sense to be used only in case the laptop doesn't work with the external monitor (I haven't try to use the ext. monitor so far) ?

I can give the motherboard to the experienced electronics, who fixed me such fuse in T400s motherboard some times ago. But in the case of T400s I found in the internet the photo of the motherboard with the fuse marked on it.

Can anybody help me to localize that fuse?



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  • Message 13 of 15

Re: Lenovo T400 very dark screen

2014-10-15, 16:54 PM
Hi everyone. I had a problem. I was trying to resolve lcd cable but after I rellace it my screen working ( I can see very bad images or start up). I was thinking it is a cream but I also had another t400 so I tested the same screen on another machine and it is working fine. Please tell me if it a mother board or inverter. If knverter where it is located and how I can replace it? Thank you everyone in advance

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  • Message 14 of 15

Re: Lenovo T400 very dark screen

2019-06-20, 7:17 AM

Does a faulty inverter cause the LCD to stop working or can the LCD just be darker?


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  • Message 15 of 15

Re:Lenovo T400 very dark screen

2020-02-27, 23:41 PM

Hi im new here, Im working on a T400 and it had 4gb of ram but only showed 2.64 usable. I put in 2 4gb and still the same.

I noticed it was a 32 bit Win -10 operating system the went in after upgrading from Win 7. I downloaded Win 10- 64 bit to a usb.

installed it, everything was great until i got to accepting the windows terms and screen went dark. Not all the way off cuz i can see light in it ..

It shows the stuff before the windows welcome/splash screen. The win 10 splash comes up and the little spinning thing and then it goes dark.

What can i do ???

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