Display Backlight not working after replacement.

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MacBook Pro 15" Retina Display Late 2013

2.0GHz, 2.3GHz, or 2.6GHz quad-core Intel Core i7 processor (Turbo Boost up to 3.8GHz) with 6MB shared L3 cache.

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Adrian Rangel @acrogenesis

Rep: 13

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Posted: May 3, 2018

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Display Backlight not working after replacement.

So I replaced the display assembly (thanks for the great tutorial), and it worked fine for 2 days but it suddenly stopped working, after some debugging I noticed that if I shine a light behind the Apple logo the screen can be seen correctly and if I connect and external monitor it works great. I've read it my be a fuse, cable or conector but I'm not sure how to test them. My board is 820-3787-06.

Thanks

Answer this question I have this problem too

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If you need a closer lookup of any part just tell me :)

May 3, 2018 by Adrian Rangel

FWIW the old screen worked before (it had damage) I connected it right now and it has the backlight problem too.

May 3, 2018 by Adrian Rangel

Tried a PRAM reset? If not, then could be a blown backlight fuse any history liquid damage drop damage? If you need board level repair, I can always help you out peep bio for that, but first thing is to try a PRAM reset.

May 3, 2018 by Brady8812

I've done PRAM and SMC reset it didn't help. It was liquid damage

May 3, 2018 by Adrian Rangel

Sounds like a board problem then. Unless you have a bad screen, but if the old one is doing it, then I'd go backlight problem

May 3, 2018 by Brady8812

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FWIW the old screen worked before (it had damage) I connected it right now and it has the backlight problem too. — Adrian Rangel
Tried a PRAM reset? If not, then could be a blown backlight fuse any history liquid damage drop damage? If you need board level repair, I can always help you out peep bio for that, but first thing is to try a PRAM reset. — Brady8812
I've done PRAM and SMC reset it didn't help. It was liquid damage — Adrian Rangel
Sounds like a board problem then. Unless you have a bad screen, but if the old one is doing it, then I'd go backlight problem — Brady8812

rholcomb3 @tarkenton Rep: 25 1 · Answer 1 · 2018-05-04T10:36:17-07:00

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rholcomb3 @tarkenton

Rep: 25

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Posted: May 4, 2018

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This shows the location of the backlight fuse. Check it with a multimeter. Should measure 0 to 1 ohm. If it doesn't, you're looking at a logic board replacement and/or component level repair.

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Ok so yesterday I investigated a little more, and using the datasheet I just uploaded:

Fuse F7700: Continuity OK

U7701 EN: 3.29V

U7701 PWM: 3.27

PPBUS_SW_LCD_BKLT_PW: 11.58V

BLKT_SD: 11.42V

LCD_BKT_EN_L: 11.4V

C7726: 5V