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68 Posts

10-04-2008

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W700 backlight issues...

2015-01-03, 4:28 AM
We have a W700 (TYPE 2757-CTO) and from what I can tell the backlight is not on.

The laptop while running seems normal otherwise. If you shine a bright light at the screen you can see the log in screen for example.

What happened: it when out a couple times in the last few days.
What preceded it: no known changes to setting or hardware.
What attempts have I made:
The screen was black (no back lighting) so I attempted to connect an external monitor to see if the video card was working and in the process the backlight came on. I used the function F7 to toggle between displays. Since the backlight came back on I assumed (perhaps) that the F7 display toggle was used accidentally and nothing was wrong - all fixed! The external display worked fine too.
Even turned up the brightness a bit with the keyboard, the W700 display seemed like it worked great.

A day or so later the backlighting stopped again. The toggle did not bring it back to a working state. External monitor and toggling seemed to get it working again.
Then I touched the laptop display gently as if to barely begin (1/8" movement) to shut it and the back light went out? Was not really really sure that made it go out or not.

The toggle and external monitor trick could not get it to turn back on. No backlight if I am in the bios either.

My thoughts: best guess is a cable or connector. I read the W700 might (or does) have two backlights. What cable or connector effects the backlighting? I assume the one from the inverter to the display?

Other thoughts: might be something else and I could be wrong, would love to hear either way. Is there a troubleshooting procedure?

Thank you in advance.

TAGS: W700, backlight, screen black
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4479 Posts

07-24-2013

Switzerland

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Re: W700 backlight issues...

2015-01-03, 12:10 PM

It could be the cable is loose (or defective in worst case)

 

You can download Lenovo's hardware maintenance manual from here: click me!

 

Then check chaper 2010 onwards, try reconnecting the LCD cable, it that doesn't work you may try replacing it, the part number is 44C5388. 


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68 Posts

10-04-2008

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  • Message 3 of 33

Re: W700 backlight issues...

2015-01-05, 0:09 AM
Tasurinchi, thank you for your response. I can see from the service manual why you said replacement is worse case.
I disconnected and connected the cable at the inverter with no luck. Jiggling the cable bit did nothing also.
As I venture deeper I was wondering what connections effect the backlights. Are the two white matching connectors on the inverter going to the backlights?
My next step would seem to be where the cable you mentioned connects to the video/motherboard. Then deeper into the LCD. I would like to avoid messing with anything other than the backlight cables and connections if possible.
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Re: W700 backlight issues...

2015-01-05, 14:44 PM

You can check if the motherboard connector is firmly attached, and also check if the the LCD works by gently pressing the back of the LCD cover, closer where the panel connector sits. 


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68 Posts

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  • Message 5 of 33

Re: W700 backlight issues...

2015-01-05, 20:14 PM
The part of the cable that goes from the motherboard to the inverter looks over heated. I would post a picture but do not see that option. I ordered a cable and took the old one out. While I wait for the new cable I wonder what would cause the old cable to fail? Cable failure, inverter or something else. Always a bit scary to plug a new cable (or part) in when you are not sure what killed the last one.
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Re: W700 backlight issues...

2015-01-05, 20:29 PM

You can post a picture using this icon :smileywink: :

 

screen.JPG


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68 Posts

10-04-2008

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  • Message 7 of 33

Re: W700 backlight issues...

2015-01-05, 20:44 PM
I do not see any of that whole interface. Perhaps because I am on an iPad?
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Re: W700 backlight issues...

2015-01-05, 21:33 PM

Could be, unfortunately I don't have an iPad, you can try posting a link to some hosting services. It would be interesting to see the status of that cable...

 

 


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68 Posts

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  • Message 9 of 33

Re: W700 backlight issues...

2015-01-05, 23:00 PM

 

This just does not look right to me...

 

W700__0.JPG

 

W700__.JPG

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4479 Posts

07-24-2013

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  • Message 10 of 33

Re: W700 backlight issues...

2015-01-06, 8:32 AM

I doesn't look so bad either. But I had broken LCD cables that looked almost perfectly from the outside... :smileysad:


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