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8 Posts

03-25-2019

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t520 backlight problem

2019-03-25, 22:33 PM

hi i have really weird problem with my t520.

If i disconnect lid wire with camera hall sensor, thinklight and led board, everything works fine backlight, clear picture everything works.

If i plug it lid wire back, i have image but no backlight. Disconnecting camera and led board not helping.

I replaced this wire 2 times, no success.

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10524 Posts

01-02-2010

US

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Re: t520 backlight problem

2019-03-26, 1:04 AM

Bad hall sensor (lid close switch).  It thinks the lid is closed.


Rich


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8 Posts

03-25-2019

RU

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Re: t520 backlight problem

2019-03-27, 18:57 PM

Nope, keyboard works normal, windows thinks it's on. Just backlight turns off.

Replaced hall sensor 2 times

Screen has image on without backlight

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10524 Posts

01-02-2010

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Re: t520 backlight problem

2019-03-27, 23:03 PM

Maybe bad cable?  I cannot think of what else


Rich


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8 Posts

03-25-2019

RU

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Re: t520 backlight problem

2019-03-27, 23:29 PM

Tested 3 different cables, 2 of them tested working from ebay

Unfortunately I have no means to test them separately. But electrically they are match, same resistance between pins and voltage on components. Camera, ledboard and thinklight works fine.

Pretty much only system board replacement left.

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10524 Posts

01-02-2010

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Re: t520 backlight problem

2019-03-28, 0:08 AM

I had the same issue several years ago on a T420 and I ended up replacing the system board.  I spent a long time screwing around with it first.


Rich


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8 Posts

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RU

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Re: t520 backlight problem

2019-04-02, 12:09 PM

I had ordered new system board, see if it fix it

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8 Posts

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RU

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Re: t520 backlight problem

2019-04-21, 0:11 AM

Yep, system board replacement fixed it.

 Really strange problem. I'm going to dig in deeper to found out what caused it and what went wrong on board.

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