Original post by: Nate ,
I would definitely go back and re-do the repair and double check that your CMOS battery is intact and working, as well as all other cables, etc. I've done repairs on laptops, missed one single cable, and had the same thing happen. The only way to fix this is start from scratch and re-do the repair step by step ensuring all cables / screws / etc are correctly installed. Worst case, you may have shorted something out (inverter?) when you turned it on which is causing it to stay off now. Let me know how you make out!