No Backlight, External Display works

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2013年末 Retina 显示屏 MacBook Pro 13"

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Deepali Prabhu @deepalip5

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发帖于: 2015年12月2日

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No Backlight, External Display works

The backlight of my Mackbook pro A1502 model is not working. Earlier it used to come on after closing lid and opening again. Now it has completely stopped. However display works perfectly on connecting to external monitor. I had given it for diagnosis at apple center and they said it was logic board issue. I have opened the mac and seen but i am not sure where the wled chip is located in this model and what is the chip number?. I have bought WLED chip LP8550 but not sure if that chip is used in this particular model I am really stuck on this issue for more then a month now :(:( any help would be highly appreciated.

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Hi,

I have the same problem. Do you have any advices for me, how to go on?

Thank you,

Martin

由 martin.joos 完成的 2017年4月1日

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oldturkey03 @oldturkey03

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发帖于: 2015年12月4日

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@deepalip5 this answer is not to diagnose your backlight failure. It is to show you the fuse and the WLED IC. The reference designator is F7700 for the fuse and it is a 3A 32V fuse in a 0603 package and the driver is U7700 and it is a LP8548B1SQ_-04 IC. Start with that and see what voltage etc. you find when checking your board. You are looking for 2.7V to 3V on pin 17 and 5V on pin 5 and 18 of the WLED driver. you also want to check the voltage on pin 1 of the LCD connector. Let us know what you find in case somebody can help you out more. Or of course, like Bradley suggested just get a logic board ;-)

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Thanks for your help. Actually i am working for an electronics company and have the tools and skilled people here so was considering fixing it ourself. The logic board replacement is way too expensive :O.

I did check pin 1 of LCD Connector and it seemed like there was a short so we soldered it again. It did not fix the problem. the indicator for water damage on Logic board is not showing red so its unlikely that its a water damage issue. Is the IC LP8548B1SQ_-04 located on bottom side of logic board?? Will i have to completely dismantle and remove the Logic board for the replacement?

由 Deepali Prabhu 完成的 2015年12月6日

Yes it is and yes you do have to remove it all the way.

由 oldturkey03 完成的 2015年12月7日

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Hi,

I have the same problem. Do you have any advices for me, how to go on?

Thank you,

Martin — martin.joos
Thanks for your help. Actually i am working for an electronics company and have the tools and skilled people here so was considering fixing it ourself. The logic board replacement is way too expensive :O.

I did check pin 1 of LCD Connector and it seemed like there was a short so we soldered it again. It did not fix the problem. the indicator for water damage on Logic board is not showing red so its unlikely that its a water damage issue. Is the IC LP8548B1SQ_-04 located on bottom side of logic board?? Will i have to completely dismantle and remove the Logic board for the replacement? — Deepali Prabhu

Bradley @bradley16836 声誉积分: 173 4 · Answer 1 · 2015-12-04T18:17:15-07:00

Bradley @bradley16836

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From the sounds of it apple is correct and it is the logic board, I have dealt with a few of these, most of them from liquid spills, although apple would have told you if it was a spill when they opened it. I think a new logic board may be in your future.

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thomasdavidp @thomasdavidp 声誉积分: 1 · Answer 2 · 2018-12-18T21:54:35-07:00

thomasdavidp @thomasdavidp

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发帖于: 2018年12月18日

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Same problem. A display corrected the issue.

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Apple ALWAYS says that a logic board is the only way to repair problems like this. There are hundreds of people around the world who repair issues like this every day. There is a wealth of information available to help if you have the desire to learn. Watch the repair videos of Louis Rossmann and Paul Daniels on Youtube https://www.youtube.com/watch?v=FIOsKc_Q... https://www.youtube.com/watch?v=5tLjQgda...

由 Peter Newman 完成的 2020年4月15日

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2013年末 Retina 显示屏 MacBook Pro 13"

No Backlight, External Display works

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