I have the original manual for my White 675 sewing machine, but it's not very clear at times. I assume this is a simple thing, but I can't figure out how to move my machine from zig zag to straight stitch. I'm doing exactly what the manual says. I don't know if steps are missing or my machine is just locked up because it's old and probably needs to be cleaned/checked by a sewing machine tech. Any suggestions for how to move the machine back to straight stitch.