I had a similar power cord problem. Sent it twice for warranty repair. The last time I had to pay for the repair since the warranty ran out. I am guessing they just did a quick fix under warranty, some new solder or something. When I had the same problem recently and took it to a different repair shop he said it was the motherboard and you know how long I waited to get it back! With no warranty the repair was about $250.
I had a similar power cord problem. Sent it twice for warranty repair. The last time I had to pay for the repair since the warranty ran out. I am guessing they just did a quick fix under warranty, some new solder or something. When I had the same problem recently and took it to a different repair shop he said it was the motherboard and you know how long I waited to get it back! With no warranty the repair was about $250.