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17 Posts

10-13-2013

Sweden

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Lenovo T400 very dark screen

2013-10-23, 23:55 PM

Hello to one & all

   

T400 -  ONE                          

 

  I have a problem with two T400 thinkpads. The first  T400 was dead when I bought it ( suspected graphics card ) . Well I managed to get this laptop to boot up. The screen was black but I found by chance that if shine a lamp or light on the screen it is working.  Now being able to see what I was dooing on the screen faintly. So I updated the bios & that did not fix the problem but I was well happy about finding out this trick. I then added 8Gb kingston ram which works with my other T400 laptops. I installed Win 7 ultimate.  The laptop is working fine. No issues  just extreamley dark screen almost black "but working"  Very strange indeed.

 

T400 - TWO    

 

 Now the second laptop was working fine. But I was swapping the parts with the non working laptop to determine the problem.  Now I have two T400 laptops with a dark almost black screen. But over about a month working on them I am making progress.  I am determind not to give up on these computers. This is not like fixing or repairing a computer. More like rezerecting a computer. I did not intend to spend so much time on these laptops but I have found a common problem that effects a lot of people. I would love to know why a  working laptop when re- assembled gives an almost black screen & still works. Normally I would just buy a new motherboard & bin the defekt one. I was quoted 150 euros from a specialist to fix a graphic problem that does not exsist, Don't get me wrong the engineer was not trying to rip me off. I would have got a new graphic processor in my computer.  I normally buy dead thinkpads fix them & sell them.  What I need is some command codes to try to make the screen brighter or any  other ideas are  welcome. Is this planned obsiletion or just a graphic defekt myth. Because after throwing away more supposidly dead motherboards with a graphic defekt  than I can count. I am starting to think that if I get the brightness back on my computers I will have sloved a major black screen problem. It is not the graphic processor. I have been playing fifa 14 with a lamp shining on the screen. It played fine, not jumpy ,no colour stripes just very dark.

 Thanks & Sorry for the long ramble        ***KANARA***

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355 Posts

01-29-2013

Greece

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Re: Lenovo T400 very dark screen

2013-10-24, 0:03 AM

HI there, it seems you are suffering from dead screen inverters, maybe you shorted out the second one when swapping parts. Look at the Hardware Maintenance Manual for the T400, find the inverter FRU and order one to test the screens.

 

I think your problems will be solved. Post back with results, help others solve similar problems.


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21115 Posts

12-20-2008

Australia, Melbourne

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Re: Lenovo T400 very dark screen

2013-10-24, 0:10 AM
Does your T400 have LED or CCFL backlit LCD? If it is the CCFL LCD then you probably broke the Inverter. But if it is the LED, you could have damaged a fuse on the motherboard.
Regards,

Jin Li

May this year, be the year of 'DO'!

I am a volunteer, and not a paid staff of Lenovo or Microsoft
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17 Posts

10-13-2013

Sweden

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Re: Lenovo T400 very dark screen

2013-10-24, 0:15 AM
Thanks big black you are a genius. I was so concentrated on testing major problems I never thought of that.
How the hell did I bring the dead motherboard back to life?
Maybe just luck.
Really thanks
I will keep you posted
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17 Posts

10-13-2013

Sweden

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Re: Lenovo T400 very dark screen

2013-10-24, 0:16 AM
Thanks Jin
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184 Posts

10-14-2008

PL

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Re: Lenovo T400 very dark screen

2014-07-16, 16:35 PM

Hi,

I've got the same problem as above - very dark screen.

I've replaced (just for try from another one) both inverter and the LCD screen. But still the screen is very dark.

What could it be?

As there're both inverter and the LCD ok, what could be the reason?

The laptop Type is:2767-AK4

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4345 Posts

07-24-2013

CH

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Re: Lenovo T400 very dark screen

2014-07-16, 17:19 PM

Did you also replace the LCD Cable?


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184 Posts

10-14-2008

PL

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Re: Lenovo T400 very dark screen

2014-07-16, 17:20 PM

Yes, I've just pluged another complete LCD assembly with no effect. Anybody can help me? Is there also in that kind of LCD with the inverter any fuse on motherboard which could fail? Or may it be something wrong with the motherboard?

I've got no idea how to fix the laptop :(

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4345 Posts

07-24-2013

CH

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Re: Lenovo T400 very dark screen

2014-07-16, 20:06 PM

My understanding is that if a fuse is blown you will see nothing, only pure black!

 

So if the screen it's dark it can be the inverter, the LCD cable or the panel's backlight itself... :smileysad:


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184 Posts

10-14-2008

PL

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  • Message 10 of 15

Re: Lenovo T400 very dark screen

2014-07-16, 20:15 PM

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.

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