No charging light and white/grey screen no logo just grey screen?

Hi,

My macbook charger broke so I looked and found some videos on to repair the magsafe charger. After the repair was complete all I was left to do was to try it on my mac. However nothing happened, no green light was lit so i figured my repair did not work. But then when I booted the laptop there was the normal grey screen but nothing after that. Then I figure it was because of the charger so I borrowed my friends working charger and plugged it in to see if it would work, but the green light never came on... The grey screen also continues... How could I solve this problem.

Thanks,