imaloony8.0

Best answer as chosen by Asker / Ratings
You've found the Fat Man? Well then, it is literally within your grasp. Walk into the room where the Fat Man was, and walk straight forward. There should be a large machine in front of you. Access the terminal in front of it, and choose the option, "Disable Status Field". Now, look where there used to be a slightly glowing blueish cylinder, and it should disappear. There is a helmet, and what looks like a square below it. That is the helmet and suit for the T-51b Power armor: The most damage resistant armor in the game. Make sure you have room for it in your inventory or a follower who can carry it, as the whole suit has a weight of around 50 lbs. As for getting out, there should be a passage right up to the main floor from the room that led into the T-51b armor room. Make sure you use your Pulse Grenades and your Plasma/Laser weapons. Those robots are a pain.

(Quick Note: If you don't have Power Armor training, you can't wear the armor. To get it, finish the story quest, "The Waters of Life" and you'll gain entrance to the Citadel. Ask Elder Lyons for permission to get Power Armor training, and around noon, the guy he tells you will train you should be around the main square. Talk to him and ask for the training to get it.
Another Quick Note: The T-51b Power Armor cannot be repaired by any armor in the game [Maybe something from the new DLC, but I don't have it, so I don't know]. The best way to repair it is to finish the quest, "The Superhuman Gambit" and talk to Uncle Roe. Invest in the caravans. If you have enough money, invest 700 caps to all 4. If not, just invest 700 into Crazy Wolfgang's caravan. The next time you see him (Wait day after day in front of Cantaburry Commons and he'll show up eventually), he'll have repair skill of 75, and will be able to repair your T-51b Power Armor to near perfect condition - for a fee of course.)