My wife has a Bernina 807,817 and it is acting up like sometimes it won't shut off when you lift your foot.
I am looking at replacing an see them on ebay for prices from $55 to $225 and they all have the same plug configuration. The have 4 holes in the plug and hers is the same shape but only has 3 holes.
Will the 4 hole one work for her model?

Dave, December 2015

You might consider opening up the foot control and removing the capacitor - on many manufacturers' machines these capacitors fail and act like a switch (short circuit) making the machine run on its own - sometimes the capacitors smoke.

The purpose of the capacitor is as a radio interference suppressor and people who cut them out don't bother replacing them.

Save money - cut the cap...

Good Luck..., December 2015