I too, would not touch the bobbin tension before doing what our friends have told you. I have a Pfaff and my bobbin was always a mess. Seemed loose and threads crossed. Now I put my finger on the bobbin as it winds and this slows the bobbin down and keeps it from wobbling. I find that if my bobbin isn't working, it's because I have the thread in the bobbin holder incorrectly. Good luck. Nothing more frustrating than having a machine not working.