Symptoms of a faulty, bad laptop power connection:

• Your power cord feels very loose when plugged into the internal jack on laptop.
• Does you power cord when plugged in "wiggle" up, down, left and right.
• The laptop only runs when you keep the power cord in a certain direction.
• The laptop only runs on battery power.
• The laptop will not charge the battery.
•  The laptop switches from AC power to battery power intermittently.
•  The unit suddenly shuts off.
•  There are no power indicators, lights, or worse, your laptop "sparks" out the back on unit.
   Or all of the above

How laptop internal power jacks break:

• Some power jacks fail under normal operation of your computer. After a year or two of usage, parts just 'come loose' on certain models. 
•  Sometimes the laptop gets dropped and the cord "yanks" the internal power jack loose.
• People, pets and vaccum cleaners all trip over laptop power cords on a daily basis, pulling, loosening, damaging the internal connection.
• The laptop is moved around a lot. After the jack is moved back and forth enough times, it comes loose.

An internal power jack on a laptop "unseats" from the solder joints, or the thin prongs snap away from the board causing the electric circuit to stop or be intermittent.
Most repair shops will diagnose this as a bad motherboard which can be a $450-$600 estimate repair by them, replacing the motherboard.
Manufactures charge $500 for power jack repair on laptops, once again by replcaing the entire motherboard. (mainboard)

In most cases, 90% of the time, the internal power jack on a laptop can be replaced, if completely broken, OR repaired. Sometimes, it can very well be a bad, faulty motherboard in the laptop. If the power connector within the laptop is completely broken, cracked, it could of "shorted" out, or power surged the motherboard. Causing damage to the motherboard (mainboard). Operating a laptop WITH a faulty power connector (if you move the power cord into the right position, it powers on, for example) can also eventually short, and damage the motherboard (mainboard) 

Depending on your model laptop, the extent of damage of the internal power connector, your internal power jack (connector) can be repaired at $125-$165

Includes part, labor, dis-assembly, re-assembly and a complete test of your laptop.

For more information:
Lightspeeds Computer Repair of Augusta
http://www.augustapcrepair.com
(Look under the Laptop PC Repair link on left side of main page)

Feel free to contact with any questions.