Will not power on

If you are sure that the power supply is fine, then it is likely that either the motherboard or the dc jack is the culprit. If you can test the board when it is plugged in, try to to see if you get voltage on the contacts of the dc jack. If you dont then you know its the dc jack and if you do then it is the motherboard.*

If you have never soldered a dc jack on a motherboard, I would see professional help. There is a copper core in each lead on the motherboard which connects it to the circuit. If the core is damaged or removed then there is very little chance you will be able to fix your dc jack.

If it is your motherboard, seach the part number online and you should be able to find a replacement, but just remember that its not always cost effective to replace such an expensive part.