Ok, I cant repair this with ANY power armor I have. Do I need something special or can you just not repair it? I have 100 in repair and the armor is under 50% each.

You cannot repair the T-51b with any other power armor. The only way to repair it is by having an NPC repair it for you. And the NPC in the game with the highest repair skill is Crazy Wolfgang. His can repair up to 85% condition only, that is, if you invest 700 caps on him at Canterbury Commons.

I suggest giving the armor to a follower as it almost never degrades. I gave mine to Charon at around 90% condition and after a few days playing, it still is.

I would. Except Charon is kinda...dead. I think that Deathclaw thought he was tasty looking. lol

Thats just lame though. I normally dont use power armor cause it might lower a special. When I found it I thought sweet, no negative effects. Oh well. I still love combat armor and I have a high natural DR due to perks anyway. Guess it doesnt matter.

That's pretty clever, Ajax.

It seems there's a special version of T-51b in the Operation Anchorage add-on. Apparently, the normal T-51b is listed as having 2000 HP (Condition) and the special version has 9992000...

That was before it was cut out of the game. It's naturally at 1000 Health, without abusing the console.

Then it would be weaker than any other power armor. It doesn't say that it's been cut altogether, only that the 1000 HP was cut.

The 1000 HP winterized T-51b can be repaired using regular power armors. So you can all relax.

Here's an interesting thing what happened in my game.
I did You Gotta Shoot Them in the Head, and handed all the keys off to Crowley. Mostly because I just couldn't be arsed to go all the way up to Fort Constantine at that point.
So I go and do some other quests, bugger about with exploring and other wastelandy shenanigans. I come out of Rivet City after selling off all the junk I'd accumulated and who do I see but Crowley, wearing the T-51b.
I do my duty - I gun him down and steal his stuff.
Serendipitous!