singer foot pedal ?

You are probably referring to this string...
http://www.howtomendit.com/answers.php?id=147215

You will notice that several people report success by just removing the capacitor and not replacing it.

I think the capacitor is there to suppress radio interference and serves no other purpose - not an issue with digital broadcasting these days.

The answer to your question is - I think - none.

Good Luck...
October 2016