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Kleiberg
Paper Tape
Posts: 1
Registered: ‎05-25-2018
Location: NL
Views: 1,504
Message 1 of 6

Cause of Y50-70 dim screen (no backlight)

Hello,

 

The title describes my problem. External screens work, as does every other part of the laptop. I had a hinge failure after which the cable connecting the screen broke. I patched it together with aluminium foil and ordered a new one. It worked for a while  with the old one but one day the laptop just spontaneously shut down, after which the backlight never went on again. Replacing the cable hasn't fixed this. 

I've tried Fn-F2/F3 and reconnecting the power supply and RAM. 

Is there a way to diagnose whether my screen, the motherboard, or a software error is causing this? I'd like to be sure before ordering a replacement screen. I read something about a lid closing switch not working properly as well, how would I check that?

 

Thanks in advance

Community SeniorMod
Community SeniorMod
Posts: 9,504
Registered: ‎01-01-2010
Location: US
Views: 1,473
Message 2 of 6

Re: Cause of Y50-70 dim screen (no backlight)

 Does the camera work?  If no, I suspect the cable that goes to the camera (also the lid sensor)


Rich


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
JDGillis
Bit Torrent
Posts: 2,901
Registered: ‎12-11-2015
Location: US
Views: 1,471
Message 3 of 6

Re: Cause of Y50-70 dim screen (no backlight)

Often the problem when the LED cable is damaged is that there was eventually a short in the cable, and the backlight fuse on the system/motherboard has blown.   

 

Unfortunately it is very small and soldered to the board, and thus is not something that can be replaced by someone other that an experienced repair person with the proper soldering equipment and skills.   The best method to desolder and resolder the part would be to use a heat station, which uses a pinpoint jet of hot air to melt the solder to limit damaging other components.    The resistors/fuses are cheap (a dollar or two) but first you have to determine if that is the fault.

 

Warning:  If testing, make sure that you have disconnected battery, AC adapter and held the power button down for a while to ensure all power has dissipated before attempting any testing.

 

I do not know what exact model you have, and thus which motherboard is installed, but I believe yours will have a zero ohm resister located next to the ribbon cable as shown below, and if it is does not show continuity (should be nearly 0 ohms) or looks burnt, it may be the culprit.    If the system was powered up, you should be getting approximately to 19 -20 volts on both sides of that 0 ohm resistor.

 

Zero Ohm Resistor (example)

zero ohm.jpg

 

 

 

Possible location on your motherboard (near screen ribbon cable)

Zero Ohm Resister.jpg

 

 

Good luck,

Altechy
Paper Tape
Posts: 5
Registered: ‎05-30-2019
Location: US
Views: 489
Message 4 of 6

Re: Cause of Y50-70 dim screen (no backlight)

Could you please provide a link where to obtain this part? 

JDGillis
Bit Torrent
Posts: 2,901
Registered: ‎12-11-2015
Location: US
Views: 486
Message 5 of 6

Re: Cause of Y50-70 dim screen (no backlight)

The part could be a fuse or resister, and it varies wildely by model, so there is no one size fits all, and the wrong part could cause other damage..      

iacopo
Paper Tape
Posts: 1
Registered: ‎06-24-2019
Location: IT
Views: 289
Message 6 of 6

Re: Cause of Y50-70 dim screen (no backlight)

Good evening, I found this post in the forum looking for a solution to the problem I'm experiencing with my notebook.
Practically after breaking the screen, I tried to replace it with a new one, but since I made the replacement, the backlight didn't work anymore.
to be sure of what the problem was I tried another 2 replacement screens and they all showed the same problem.
reading the solution to the problem I can attach the photos of the motherboard in question, if it were possible to know which of the visible resistances or fuses is the cause of the problem I could try to replace it.
MODEL MB: LTS-2 MB 17812-1   448.0CW18.0011  //  Notebook : TP00085B    P/N: SL10Q74783

Thanks in the meantime for the help you give me and I apologize for any incorrect English but I'm using google translator.

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