Hello Jenny,
When you look at the bobbin case area and you turn the balance wheel, does the raceway move? that is the part that the bobbin case sits in, the bobbin case itself does not move so don't be confused, if the raceway is moving and the machine is not picking up the thread the first thing to do is change the needle and make sure the flat side is facing the back of the machine, it only has to be slightly bent and it will miss stiches, should not get any major problems with that model, if you do you can e-mail me at drivewithken@blueyonder.co.uk make sure you mention your model again because I get a lot of sewing machine questions, I don't go back to old questions on this site to see if there are any answers. I will find a site that has a book.
Ken
drivewithken@blueyonder.co.uk, October 2007