Hi.
How did the motorized sewing machines controlled their speed, before thyristors ?

 

The very earliest ones used a Universal motor and a variable resistance operated by the foot pedal.

 

Which reminds me, my wife has an old 1950s era sewing machine with a switch for Low speed/high speed. It recently started to lag and shudder before starting when on "low" setting. Time to open it up to see what that switch is doing. I'm guessing the switch disconnects one of the diodes in a bridge rectifier or disconnects one of two anti-parallel SCRs.

 

Hmmmm.... no silicon diodes in the fifties... Try lubrication everywhere.

 

I worked in a factory full of sewing machines...Swiss, Chenille, zig zag etc...and they all used the slip on the drive pulleys to control the speed.

 

The Universal motor and variable resistance F.P. was back in the late 50's to 60's. in the UK.

 

I remember a singer mom had that had a wirewound rheostat and the pedal moved a wiper along it like one we had a science class in school.

 

I remember a singer mom had that had a wirewound rheostat and the pedal moved a wiper along it like one we had a science class in school.

As per post #2

 

Wife and I ran a drapery work room for many years. As the market moved from soft to hard dressings, we sold all those machines. 20 years later, there is a resurgence in demand, so we are looking for good used machines to restart a workroom. Hard to find and expensive.