MacBook Air wont turn on, capacitor damaged, motherboard repair

Ok thanks for your help. I have removed the schematics, I did not knew this was copyright material. I will order and replace.

@dean88 Have you checked to make sure the line isn't shorted anymore (I assume it was to begin with). Even though this capacitor is marked as critical on the schematic (and I would replace it regardless since it would be fairly safe and easy to do so), I would still think it should power on without it. Even if it would be better for it to be present.

I would make sure there's no short to ground still on that power line. But those tantalum caps are frequent points of failure.

@flannelist Thanks for your comment.

- I used the multimeter in continuity mode and I noticed the capacitor was damaged and shorted because it gave a continuity beep.

- Then I removed the capacitor and I tryed to turn on the macbook without the i/o board but nothing happend.

- I have ordered new capacitors of the same type.

I am sorry but I don't know (yet) howto test the line for no shorts, if you could explain of push me in the right direction, you will be a big help!

yesterday by Dean88

@dean88 Sounds like you're on the right track. And by the looks of that cap, it may well have been bad.

But based on the fact that you're still getting no power (I would expect the removal of the cap to relieve the short and allow power on, even without replacement), your underlying issue may be elsewhere.

To test if that line is still shorted to ground you can use either diode mode (if your multimeter has that) or resistance mode. To use Diode mode, put the red probe on any ground on the board, that gold spot near the bad cap would be an obvious choice. Then check with the black probe the readings you get on both pads the cap was on. The one closer to the fan connector should beep (or read close to zero) because it's ground, but the other one should not. I got a reading of .147 on my multimeter with a known good-ish board.

Resistance mode is similar, but takes longer to get a good reading. You'll want black probe on ground for that one and red probe on the pads. But same idea. Close to zero=still short

@dean88 Also because I ran out of room in my last comment. Did you test the cap while it was still on the board? Because that can get you into trouble with shorted lines.

If the whole line is short to ground, then a cap would read as continuous. But what that actually means is, they're both continuous with ground. Sound logic, in theory, have made that mistake myself. But measuring caps is better done when removed from the PCB.