MacBook Pro - No Power

I have a 14 month old Macbook Pro A1278. About 2 weeks ago, the magsafe adapter no longer seemed to work, but was still running on battery. As I needed to use my computer, I continued using it till the battery died knowing that I could borrow a work colleagues power cord the following day. When I got to work the next day I borrowed my colleagues cord but still no power so I tried another colleagues cord and same thing - no power. I opened the back of my Macbook and disconnected the battery and tried all 3 cords again, still nothing. So I assumed it was the magsafe DC connected which I replaced with a second hand one (exact same part - known to be working), but still nothing. I am at a loss, what else could it be????