I have an elderly New Home 580 which I set up to use for the first time since moving yesterday (last used at Christmas). However it doesn't seem to be powering the needle properly. If I loosen the drive wheel, as if to load a spool, it runs normally but if I tighten it to sew it barely moves the needle even at full pressure on the pedal which then causes the motor to spark Typically I can't find the manual atm and no info online. Any ideas please ?