I have a number of Berninas, 930, 150, 160, 430, 200 and just traded an 830 for a 790. It was my understanding that none of the Berninas work with prewounds. I know the 830 and 790 are specialty bobbins. Are you using a prewound on a Bernina?, if so, what model do you have? Yes, I am a Bernina freak. I am sewing machine poor!