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Laptop screen doesn't work unless I plug in then unplug an external monitor

Posted on 2014-02-04
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Last Modified: 2014-02-27
Hi fellow techies,

I have a really odd customer laptop in at the moment.

The customer brought me her laptop to replace the screen hinges (she later told me that it had been dropped).

I replaced the hinges, all good as new. I tested it and got nothing on the screen so I plugged it in to my KVW switch and it sprang to life, I unplugged it and it was working perfectly on the built in screen so I shut it down and got her to collect it.

She got it home and the screen was blank, so she brought it back, any how, I have discovered that all I need to do to MAKE it work is to plug in my KVM VGA plug and remove it again. It never works on it's own, the problem remains identical and the fix always works.

Before I set aside an hour or so to strip it all down and check for internal damage from the fall, etc. has this ever happened to any of you and if so, what was it?

My guess would be that it is something to do with grounding. I can't remember whether the internal video cable had a ring connector to screw down on or if it is CCFL / LED unfortunately.

Thanks in advance!
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Question by:allisolve
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by:
The_Warlock earned 250 total points
ID: 39832764
Have you verified that it is set to output on the correct monitor and not the secondary output display under the display settings? Unless physically checked I would say that its not a grounding issue. If it was it  would more than likely not work at all either way.
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Assisted Solution

by:allisolve
allisolve earned 0 total points
ID: 39833109
Yes, the output selector button does nothing. Also, as I say, the only intervention needed from me to get it working is to plug then unplug a screen in to it. I don't have to select the source. Also it does that automatically as it comes up on the external, then the internal. Thanks for your input though. Much appreciated!
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Expert Comment

by:nobus
ID: 39834914
can you boot into the bios - and see the screen?
also -  when you have a screen, check what closing the lid should do
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Author Comment

by:allisolve
ID: 39836085
I can't boot into BIOS without using the external monitor and my little trick only appears to work in the Windows environment.

What I have noticed is that when it is first switched on the screen lights up and there is a flashing underscore cursor at the top left for a few seconds then normally when it would show the logo screen with the option to press F2 it goes off and only comes back by using my little trick and only within Windows.

Closing the lid makes it go to sleep but the screen doesn't work when I open it back up again without plugging in then unplugging the cable.
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Expert Comment

by:The_Warlock
ID: 39836249
How old is the laptop? So, when you power it on does it seem like it boots normal but you just can't see the boot process? Have you tried holding a flashlight to the dark screen to see if you can see the boot process and or windows desktop after its booted?

To me it sounds like either a backlight or inverter board issue. If you can see txt on the screen while holding a flashlight to it then its more than likely one of those two things. Let us know what you find. Hope this helps.
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Assisted Solution

by:nobus
nobus earned 250 total points
ID: 39836278
>>  Closing the lid makes it go to sleep  << i would turn that off to start with
also check the bios settings
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Author Comment

by:allisolve
ID: 39837370
The_Warlock:

It says 11/01 on the sticker, so just over 3 years old. It is an eMachines E442 and all but one replacement screen I look up are coming up as LED. I need to strip it again to make sure I didn't miss something, so I will have a look to see if it is LED or CCFL.

I haven't tried using a torch to look at the screen as I didn't have one really handy earlier. I have looked very hard at it to look for changes on the dark screen (I can normally see shadows when it is a backlight problem). I could see no movement.

Yes, it does boot normally other than the screen crapping out.

I did notice that the external monitor was getting dimmer then brighter, etc earlier so I am wondering if the GPU needs reballing or something.

nobus:

I will give that a go. I looked through the BIOS earlier and it all looked ok. I was going to have a look see for the latest BIOS to flash it with too, but it just bothers me that this is all since it was dropped, so I am drawn to that being the cause. It could just be a co-incidence though!
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by:nobus
ID: 39838141
i would try reversing the changes in the bios - just to test it
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Author Comment

by:allisolve
ID: 39840467
Do you mean load defaults?
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Expert Comment

by:nobus
ID: 39841229
no - just note the ones you change. defaults does not tell you which ones changed
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Author Comment

by:allisolve
ID: 39841724
Oh, I didn't change any settings, I just looked through and there weren't really many settings that could be changed and everything looked ok.

It has just started working perfectly now though and has worked every time I have tried it for about 20 attempts now.

Puzzled and a little worried, but I don't see what else I can / should do at this stage.

At the end of the day, the job I was paid for was replacing the hinges. I did that and then discovered a further fault, but it had nothing to do with my original repair. It has after all, been dropped hard enough to totally snap a hinge, so god knows what other damage was caused in that fall.

Thank you all for your help though. As always, very much appreciated!
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Expert Comment

by:nobus
ID: 39841873
if you don't need more help - dont forget to close this
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Author Comment

by:allisolve
ID: 39877725
How do I close this??
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by:nobus
ID: 39878881
you can find all details on closing in the help files
but in general -  you accept one or more answers that helped; if none helped, choose yours.
or delete the question
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Author Comment

by:allisolve
ID: 39879143
Surely with this number of amazing techies you could add a close / delete button to the page so as to make things a lot easier?
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Author Closing Comment

by:allisolve
ID: 39891387
All good ideas and things to try, but ultimately nothing in this thread resolved the problem. It went away for a while, but my customer has said that it has started doing it again. I am sure that there is some physical damage to the motherboard from the fall.

Thank you all for your input, very helpful and reassuring as usual!
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Expert Comment

by:nobus
ID: 39892082
tx for feedback
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