My sewing machine foot pedal will not switch off the motor?

I have an old PFAFF 30 electric sewing machine. it works with a foot pedal. It has a Sew Tric motor and presumably a Sew Tric foot pedal.

Recently while using it, something 'popped' (like a fuse blowing or short circuit) and the machine would not switch off when the foot was removed from the foot pedal. The light stayed on and everything was in action, except the way to stop it.

Inside the foot pedal is a silver tube with wires at each end. One end is attached to the neutral terminal the other is floating free. I cannot see where it would have been attached, although it does reach the live terminal and has a loop of wire on the end. I am wary of attaching it to the live incase I do more damage. I think the silver tube might be a noise supressor or a capacitor of some kind. The power still gets to the motor and the machine bursts into action when switched on at the wall but cannot be turned off, except at the wall socket. can you advise what might be the cause and how to remedy it. Otherwise the machine is in good working order.

Andy Gammon
April 2014