Dead short on power jack

Should be battery first, Then AC adapter (Charger)

Dead short on DC Power Jack?
Are you aware of how a DC Power Jack is made, (Component structure), and how it attaches to the motherboard?

If not, allow me to explain. This is an example of an average DC Power Jack,
http://us.st12.yimg.com/us.st.yimg.com/I/yhst-42877593004970_2046_1336946

The outside housing of the DC Power Jack, is barely larger than the outside of the AC adapter (Charger) plug.
It's about a 1/4 inch wide, 3/8 inch inch tall, and 1/2 inch long.
The body is made of plastic.

The outside shell opening in the body is the Negative contact.
The pin in the center is the Positive contact.

Those flat metal prongs, or pins, you see in the photo, go down through the motherboard, are are soldered on the bottom side.
The photo of the jack is upside down, in relation to how the jack sits on the motherboard.

When the 'Charger' plug is plugged into the power jack, it can get bumped. A hard enough bump, or repetitious bumps can damage
the center pin mounting, break the outside metal shell loose, and/or break the plastic housing.

It can also break the solder joint/s for those flat metal pins.

AC adapter unplugged from the laptop, battery removed, see if you can take a pencil eraser, and move that middle pin around. You may see the entire jack move.

There is also a large number of laptops, made with a defective motherboard design. To explain, I'll have to give you a crude example.

Think of the laptop motherboard as being a 1 foot square. (It isn't. It's irregular shaped)
Now along the edge of the 1 foot square, attach a 2 inch square.
It's actually all one piece.

Due to accidental bumping of the 'Charger' plug while in the power jack, this 2 inch 'Peninsula' can break away from the main body of the motherboard. (1 foot square)

There are circuit traces on the motherboard. (Think of a circuit trace, as a Very, Flat, Thin, copper wire)
These circuit trace can become stretched by the cracking, or breaking away of the 2 inch 'Peninsula'. They can then be exposed to circuit traces they're not designed to touch. This can cause a direct short.

(Also, due to the bad design of these motherboards, the laptop user can be just using the 'Charger', in an everyday situation, and this 2 inch 'Peninsula' can break.
Just by plugging in, and unplugging)