you are right it sounds as if it is the dc socket. on most machines at the best of times it is quite hard to solder the dc connection points to the board, you have to be light handed or you will burn/solder straight through the motherboard rendering the board useless.
my theory is if it is the first time you have paid out on the machine get it fixed .....if not sell it on ebay for spare parts
average prices for eg. screens 50 plus (depending on size and condition). keyboards 20 plus. adapters 15 plus. cpu's 20 plus. and battery 20 plus...good luck
the workshop
August 2009