Sony Vaio no power at all

Hello,
I have a Sony Vaio PCG-7173L laptop that won't turn on. It first started having problems charging, I had to wriggle the DC jack about for it to charge, the problem got worse and worse until one day I just couldn't get it to charge. I have tested the charger to be sure and it isn't the charger, it sounded to me like the DC jack was broken so I ordered a new one and it arrived today and I replaced it. Still it won't charge. I might also add it also doesn't run without the battery in, just running off the mains. Is it possible the motherboard is dead? I thought it would be unlikely. Any suggestions? I have a multimeter.