Here are links to a couple I unfroze:
http://www.quiltingboard.com/picture...c-t162425.html and
http://www.quiltingboard.com/vintage...r-t169127.html
But before you mess with it open it up and see if there are any plastic gears - if so, are they melted, cracked, clogged up or missing? Plastic gears are not too hard to replace - info on this board.