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Backlight not turning on. Thinking it may be a capacitor.

Hey y’all I’m new to max repair. I opened up the MacBook Air (2017) and found a corroded capacitor. Cleaned it up a little bit but I think that this capacitor may be the reason the backlight isn’t turning on and am looking for a little input if this could be the issue. Also wondering how I can find the right capacitor to replace it with. I’ll upload a picture below from before I cleaned off the corrosion. I’m referring to the capacitor to the right of the display port with green corrosion on the right side of it. Thank you

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Michael Sampino The corroded capacitor is reference designator C7797. It is a 10uF 50V 10% capacitor in a 1210 case. It is part of your backlight driver circuitry. You could check it for short to ground. I'd replace it anyway since it does show corrosion on it. As for your backlight, just test it on the LCD connector. Place your multimeter in diode mode. Red probe on ground and black probe on either 3 or 4. Pin 1 starts closest to the particular capacitor. Let us know what you get. As for voltages , Black to ground red to pins 3 or 4 and meter in volt mode, you should get around 27V or higher on a good working system, Again , let us know what you get.

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Testing in diode mode following your instructions I got 0.001. And then when testing for voltage I got 0 volts.

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Would this mean that my issue is a blown fuse?

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Definitely sounds shorted. Looks like a weirdly localized bit of corrosion if that’s all there was. Not unheard of, that whole area is super typical for liquid damage. But it would be weird to me if that little spot of corrosion killed the cap (not impossible but I would be surprised).

Also. Is it just the picture, or is the one sort of perpendicular to the corroded one, just underneath it have a crack in it? It could definitely be the picture. But cracked caps are a sure cause of a short to ground.

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Yea the original damage was from liquid damage. Originally the MacBook wouldn’t boot but now the only issue I have is the backlight (I’ve been hooking it up to an external display at the moment). The cap perpendicular to the corroded one was not cracked. Must’ve just been some dust on it when I took the picture. I’m going to go ahead and order a new cap and fuse and replace them and hopefully it will fix the issue. Thank you for your help.

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Great job--you found a shorted line! The likely cause is indeed this cap, although there could be others on the back side of the board. Remove and see if the line is still short with the multimeter. If not, then you can leave it off or put on a new one. You will need a powerful hot air station, so it's a bit of a challenge. The downside to leaving it off is only that you may have a little backlight flicker. The downside to replacing it is----needs experience and fancy equipment---you could make things worse trying to replace it. Up to you!

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I’d check the two filters as well (grey square with two connections) on a iPad resistance is around 0.14 ohms so hopefully they’ll have about that. They are usually backlight filters on iPads so maybe worth a test as well.

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.15 ohms so the filters should be fine. Thanks for the advice

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No problem, good luck.

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