Take out the bobbin, bobbin case, drop the gate down and take out the hook, see if the machine will turn, if it does then something is stuck round the edge of the raceway possibly a small piece of thread, if the machine does not move at all but you can wind a bobbin then it will be a process of ellimination to find out where it has jammed, look at the gears after taking the bottom off the machine to see if they are broken.
drivewithken@blueyonder.co.uk, January 2008