I have four kegs, two of which I got a the LHBS and have been working out great. The other two I got off of eBay and for reasons I can't figure out, it's about impossible to get a disconnect on or off of them. To get them on I had to tap them down with a hammer, but then of course trying to get them off I ended up having to pry the disconnect off and broke the disconnects.
The posts look fine to me, I don't see any dents or other issues with them. I've given up on them and decided it's best to just scrap the whole post assembly and start over.
Northern brewer sells the assemblies, but they have three different ones.
Type A plug assembly fits Firestone V, VI, Challenger and Super Challenger kegs.
Type B fits Cornelius Spartan, Super Champion and 'R' kegs.
Type C fits John Wood 85 and older Firestone Challenger kegs.
How do I know which one I have? All I can tell from reading it is that it was the property of 7up bottling co in flint michigan and it says cornelius company on the side. If it says Cornelius on the side would that make it a Type B for sure?