Button Foot Controller Repair

My Singer 401 has a button foot controller which I use by way of a knee bar. Until recently, the 401 had one speed – 100 m.p.h. It was polite enough to wait until I pressed on the knee bar before it started sewing. But, once it started, it went flat out all the time. E took it apart and fixed the problem and I thought I'd share how he did it.

You'll want to take a look at what Sid had to say about button foot controllers in his February 22, 2012 post at http://oldsingersewingmachineblog.com. Sid explains how the controller works and he has some great photos of the inside of the controller which will be helpful to you as you keep reading this post. (Thanks, Sid!)

E unscrewed the little feet on the bottom of the controller and took the top off the base. Someone had already removed the capacitor from between the two terminals, so it wasn't causing a problem. As you can see from Sid's photos, there's a screw which runs all the way through the white porcelain case which contains the variable resistance. The tip of the screw pokes up toward two little rectangular copper contacts and has a little plate attached to it. The little plate that's attached to the tip of the screw ought to touch the copper contacts when you have the button on the foot controller pressed all the way down. This gives you a resistance-free path from one terminal to the other and this is what gives you full speed.

When E looked inside my controller, he saw that when he pushed down on the t-shaped lever the button sits on, the little plate was touching the copper contacts well before the t-shaped lever was pushed all the way down. This explained the 100 m.p.h. speed.

To fix the problem, E slightly turned the screw clockwise which moved the little plate lower on the screw. He kept turning the screw until the little plate was barely touching the copper contacts when the t-shaped lever was pressed all the way down.

The button controller is back in the 401's cabinet and it works great. If you're having a similar problem, you might want to grab a screwdriver and give this a try. Happy Sewing!