how can I unjam my singer sewing machine? (I don't know the modle)?

Sounds like a massive thread jam to me. Did you forget to put the presser foot down before stitching? Anyway a piece of thread 1/4 " long can cause this. Get your long tweezers, and some scissors that will cut threads between the presserfoot and needle plate. Cut threads and gently tease them out; don't try to sew until free motion is achieved. I usually have to remove the needle plate and the entire bobbin case clip, pull, brush, clip pull brush, etc., until everything seems to be thread free. While everything's apart, wipe all with your oil-dabbed Q-tip. Put everything back together. Use a freshly wound bobbin, a new needle and rethread the machine from scratch. If it won't sew, go back and find that last bit of thread. If it's not perfect, perhaps it will stitch enough that you can adjust the tension (www.sewalot.com).

Galey
June 2006