This manual is really helpful:
http://www.tfsr.org/publications/tec...achine_manual/ They did a really good job writing this one. I love it I live by it when I've got something on the bench. Go through it word by word, step by step and you can fix a tension. I had a couple 15 machines that I had to rebuild the tensions. It was tricky getting them fussed out but with the help of that manual I did it. One needed a new spring the other needed the old spring free of oil and gunk. I do not know why anybody would ever use 3 in 1 oil...