If there is no power going to the laptop itself(or even charge the battery) while plugged in, its probably the DC Jack which can be as expensive to repair as buying a new system(PC shops charge alot since you have take the laptop apart and resolder the Jack). Does the plug wiggle at the laptop? If it does then it's a good bet that it's the DC jack.
Replacing a motherboard in a laptop is also the same result. The time and money spent could be used on a new system. Good news is, the hard drive could still be good so an enclosure will be all that's needed if you need stuff of the the drive.
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