Why won't my Xbox power on?

Well, after a power surge while I was away from home, my Xbox wouldn't power on. I knew it was the power supply because it's meant to do that, to protect the other components. But, even after buying a new one off this website for $20, I have replaced the power supply and it still won't turn on. I followed each step by step and finished. But it just won't power on. I've tried the socket, yes it works, the cable doesn't appear damage (plus I used another one to test), but the console won't make any noise or power up whatsoever. What do I do?