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What do you mean by the AC jack? The Magsafe cord that is detachable or the part where the actual brick is at?
 
I think you are talking about the actually AC jack that is soldered onto the logic board.

I have replaced many AC jacks on PCs, and its really rather simple if you know how to solder. As for a magsafe AC jack replacement, I have never heard of one breaking since the cord would unplug before an stress could be placed on the jack.

I would guess that something else is wrong with your logic board (other than the jack) or is just the power adapter that is bad. Good luck!
 
If you're talking about the socket on the laptop itself that the external cord plugs into, that's integrated into the machine itself; you CAN replace it, but it takes a lot of doing...
 
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