I have more than one 1950s and 1960s era Singer sewing machine in my life. These machines are about as good as it gets in terms of straight line sewing, they don't have fancy stitches like a modern machine but they are tough as old boots and will outlast us all.
Sadly there are a few parts even on a '50s Singer that won't outlast us, in fact they're failing here and now. I'm talking about the suppression capacitor in the motor controller, which after sixty years of service is now in most cases reaching the end of its life and failing. You plug in the machine one day and it starts up all of its own with no foot on the button, there is a horrible burning smell, and smoke comes from the foot controller. You have two choices if you want to keep the machine running, buy a modern electronic controller from a specialist Singer spares supplier, or fix the original. It's the latter course I'll now describe.
|Cover off, dead capacitor with brown gunge.|
The capacitor is a pretty standard mains suppression capacitor, a 0.1 microfarad item with a 250VAC rating. It's the voltage rating that's the important bit rather than the capacitance, use a lesser rated one and expect fire. Happily these are easy to order and don't cost much, you are looking for one described as "Class Y", or sometimes Y1 or Y2. Mine came from Farnell, but you can buy the same from almost any other electronic supplier. Make sure you pick one with decent lead length though, as you'll see you need those wires.
If you open up the Singer foot control by undoing the four screws on its bottom and gently prising it apart, you'll see the problem immediately. On top of the ceramic rheostat housing is the silver can of the capacitor, and if it's failed you'll see plenty of brown gunge spilling from one end. Be careful of this gunge, it's probably quite harmless but you don't know quite what chemicals went in to '50s components.
|New capacitor in position.|
Then take your new capacitor and carefully bend its wires to fit round the screw holes in the same way as the previous one. My capacitor fitted neatly in the recess in the ceramic, as you can see in the picture. Be careful to ensure it doesn't foul the mechanism beneath it.
I've done this with all my machines, even those whose capacitor hadn't failed. Preventative maintenance makes sense, in this case.