The ruined machine was barely functional.
I don't think ruined works, but I can't find a good antonym for well-kept or well-maintained.
"The abandoned machine was barely functional" could work, but then again it's not a direct antonym of well-maintained or well-kept.
Hello gmloft, You can consider "dilapidated". Best wishes, Joseph
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.