The capacitor in the foot switch has blown. It is rated at 600v DC Wkg and 250v AC Wkg. Unfortunately the capacitance cannot be seen as this is where the case has melted and split. The only other marking on the case which can be read are HUNTS A4038H

Phil Standley, February 2010

Hello Phil,
Take it out and throw it away, you don't need it.
Ken

drivewithken, February 2010

A little further searching has found extensive post

http://www.howtomendit.com/answers.php?id=147215
"Old Singer foot pedal problem?"

Nick Dyson, February 2010

Don't know about 15K80 but my wife's elederly Singer 328K did the same thing this week. I removed the capacitor and enabled her to finish her task.

Capacitor has written on it:-

HUNTS
Cap. 0-1uF
250v A.C. Wkg
M.P
WA 71 1AI

Assume that's 0.1 micro Farad

According to earlier post the machine can run without it!
http://www.howtomendit.com/answers.php?id=178400

Nick Dyson, February 2010