Okay.. half the brewing season shot to hell and my second batch down the garbage disposal.
At the beginning of the year, I emptied out a keg I had homebrew soda in. The soda had been there (refrigerated) for about a year. I soaked the keg in hot water, sanitized and couldn't notice any smell. I didn't have the 7/8 socket to remove the posts - big mistake.
I put my Octoberfest in that keg. Two weeks later, it had a sickening, sweet off-flavor. It was so bad, I had to toss the batch. I thought it was an infection from the keg. The bottles from that same batch tasted fine - so, no Octoberfest this year
I sanitized the keg again, this time overnight - (still didn't remove the posts; stupid me) and I replaced the rubber. I also replaced the beverage draft hoses. I got "food-service" hoses from home depot and put them on both of my kegs. But two days later, both beers tasted like plastic - so I trashed those hoses and put new ones on from the HBS again. I put my brittish bitter into that keg and a week later, got the same off flavor. I thought it was mild enough that I could save it. I racked the whole thing into another keg and replaced the draft hose again.
NOW - I got the socket and removed the posts. I threw out all the rubber and poppets and soaked all the metal in brew-r-ez overnight. Then I replaced all the rubber and poppets. I just racked my hopback amber into that keg and it's pressurizing now. Hopefully it will be okay.
I just tasted the bitter, and guess what - same off-flavor, only it's seemed to have grown stronger. I dumped that batch and disassembled that keg - that was my good keg. It's all soaking in brew-r-ez overnight. I guess I should replace the draft line again. This off-flavor is literally following me.
BTW, the main source of it was the original keg w/ the soda. When I removed the posts, the out post smell almost knocked me over.
Moral of the story - don't skimp on cleaning.
I'll be REALLY pissed if my hopback amber is ruined - it tastes great now