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No backlight + no keyboard backlight implies fuse problem?

I have had display problems, so I changed the backlight fuse on my Macbook Air. After that, there is still no display. The computer works fine otherwise, I can turn it on and hear sounds.

As of now I am wondering whether I soldered wrong, or whether the problem is with the backlight itself.

I also noticed that there is no keyboard backlight. Even if I hit the keyboard backlight keys, it doesn't light up.

I was wondering whether that means that my soldering is wrong, or not. Is the backlight fuse also "protecting" the keyboard backlight ?

Answer this question I have this problem too

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If both the screen and keyboard aren't lighting, the issue will be with the backlight boost circuit (most likely the backlight IC).

You would require a schematic and board view for your particular board to diagnose this (board number etched on board, Google to find the files). You will also need a multimeter to measure the backlight output voltage (to see if this is the issue) and a hot air station (if it is a backlight IC problem, since it is a BGA chip).

Get the files and equipment if you think you can do it, then let us know when you are ready to check this. If you feel it may make the situation worse, it may be best to send it to someone who fixes these on a daily basis.

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@reecee thanks a lot for the swift reply ! I have tried reading some schematics and finding board views but never really succeeded. I also don't have a hot air station.

Is the backlight boost circuit on the motherboard, or in the display assembly ? Would replacing the whole display assembly solve it ?

I am asking because I was thinking one other way to test this was to plug another display assembly and see if it lights up : http://apple.stackexchange.com/questions...

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The backlight boost circuit is on the motherboard. You can plug in a new screen assembly to check (sometimes the screen PCB can be burnt and causing the problem), but it's highly likely to be the circuit, unless you spilt liquid onto the screen itself.

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You would need a hot air station to replace the IC, have you measured the voltage on the fuse yet?

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What is the history of this MacBook Air? They rarely fail on their own. Was it liquid damaged?

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@reecee thanks a lot for your answer. I'll check by plugging my Macbook Pro's screen instead, but I am afraid to damage it by doing that, so if I can diagnose in another way, that would be great. I haven't spilt liquid onto the screen, but it is damaged. I arrived to this problem because it wasn't operating well, having flickerings on horizontal lines, sometimes scaling only one third of the screen to the whole size, sometimes not displaying at all. So I opened it up, but made things worse :(

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