machine will not make stitches?

Hi, I have a Alegro machine, yes an old one, picked it up second hand, got it home sewed like a dream, then the belt broke, I replaced it, again sewed like a dream, then the needle hit the foot which had worked loose and from then on wont make stitches, only very few and very far between, have tightened the foot, have checked the bobbin for correct tension, have even checked the tension for the material it will be running, but still not working right, any idea? thanks for reading