Hi, it's difficult to see the traces on the board, could you take another picture with more light.
I'm sorry for the very slow reply, I was away from home for work reasons. I've taken a better photograph.http://s30.postimg.org/nkyi02pgh/ux21.jpg
You can see the centre-bottom pad is missing and I've soldered a wire to where the trace ended. I've tested this with a multimeter and this now shows conductivity between the centre-top and centre-bottom pads.
I have also confirmed that DC is getting to the board by scratching away a tiny portion of solder resist and measuring 19V.
At the connector for the battery I only see 1.8V, which is surprising as I'd expect higher there. The battery is a 7.4V Li-polymer battery.
I am still seeing the exact same issue however: the laptop's charging indicator (led going orange) does not show, it instead stays green (battery fully charged).
I have removed the main battery, and also the CMOS one hoping that this would resurrect the laptop but to no avail.
I've read that there was an issue with some UX31a's coming out of standby and that by holding down the power button for > 30 seconds this would sometimes clear the issue as it presumably cleared CMOS. I've tried this of course and no improvement. I'm also sceptical that this issue should show up at the exact same time as replacing a broken DC socket.
Any suggestions appreciated. It's impossible to find a replacement motherboard for this otherwise I'd probably just bit the bullet and buy one. I will have no luck on a warranty repair as I've done the jack repair myself, and had bought this second hand.