A) Check the DC Power Jack.
The DC Power Jack is the jack that the AC adapter (Charger) plugs into. (May state DC_IN near the jack on the outside of the laptop case)
IF, I have it right, there is a DC Power Harness. The DC Power Jack is connected to wires in a harness, and the harness has a plug on the end. The DC Power Harness plugs into the motherboard.http://www.laptoppartsexpert.com/i-131440-dc-jack-w-cable.html
[Instead of the DC Power Jack being soldered to the motherboard]
Remove the DC Power Harness, and with a multimeter set to OHM's perform a continuity check of all wires in that harness.
See if the DC Power Jack of the harness, is in good shape.
DC Power Harness checks out?
Problem is with the Power MOSFET's on the motherboard, or a ceramic capacitor, or two.
Don't know who makes the P.MOSFET's on the motherboard, or what manufacturer number they are.
They are however, located Near the connector on the motherboard for the DC Power Harness, and they have 8 J-leads.
This is an example of a Fairchild Semiconductor FDS6675BZ
Power MOSFET. One example of a P.MOSFET used in this application, on a LOT of laptops,https://docs.google.com/viewer?a=v&q=cache:oER5NNz8cwcJ:www.fairchildsemi.com/ds/FD/FDS6675BZ.pdf+Fairchild+FDS6675BZ&hl=en&pid=bl&srcid=ADGEEShOhWPjm_M-ROHme4iEMrztCTOd-28jNiy1hVLQQh_VOyv8zcXEVDB_iTQA6MuZO88UmRkDgjyW9j4CP2aIJ-4DS-h6JNM3lvxldeApQeecmz_DADCw1s7tmNLxfPknqX14SZP6&sig=AHIEtbS_rYUAeo_8rB9YHkW05ZjLqeH4Jg
Note the leads coming off of both sides. Those are 'J-leads'.
See if any of the Power MOSFET's, or Ceramic Capacitors, are burnt, and/or bubbled.
This gives you more information, but is using HP Pavilion dv6000, and Pavilion dv9000 series of Notebook PC's, as an example,http://mayohardware.blogspot.com/2010/04/important-parts-on-dv6000-and-dv9000.html
Here you see the two Power MOSFET's used. One on top of the motherboard in the power section area, one on the bottom of the motherboard.
Looking at the second photo with the Alpha and Omega AO4407, Power MOSFET as an example, look to the right of the yellow circled AO4407.
To the right is a Ceramic Capacitor.
Rectangular in shape, and looks like there is a black wide band across the middle. There are two more above it. See if one, or more of these are burnt.http://www.mouser.com/Search/Refine.aspx?Keyword=FDS6679
That's right. A Fairchild Semiconductor FDS6679 Power MOSFET is $1.01 USD, without tax, and shipping.
Just an example of cost.http://www.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors/Multilayer-Ceramic-Capacitors-MLCC-SMD-SMT/_/N-b2cj?P=1z0ynasZ1z0vhw8
Scroll down. Average cost is from 9 cents to 80 cents USD.