Motors

Wiring Sew-Tric

Sew-Tric motors are found on many sewing machines sold in Britain in 1950s, 1960s and 1970s. They are good quality conventional brushed electrical motors without electronic components, so they are heavy and they don’t quit working to this day. But after some 70 years, they often could use a clean or perhaps a change of carbon brushes. For a look inside a motor, see this previous post, but here we’ll just focus on wiring the connector.

Sew-Tric motors, as well as some Hillman motors, are equipped with a 4-pin connector with the pins arranged in an arch. There is also a lamp mounted on the side of the motor.

The connector is mounted to the casing of the motor and may be on top of it or on the underside. On Hillman motors it may also be parallel to the motor axis rather than perpendicular to it as in this photo.

Regardless of the orientation, the wiring scheme remains the same. It is normally embossed on the lid of the connector.

The earth pin is thicker than the other three pins and is screwed to the metal casing, so it’s easy to spot.

This is the socket, and, just to avoid any confusion, it is male because it’s got pins. The plug with the cables going to the mains and to the pedal is inserted into the socket, but still it is female because it’s got holes that the pins go into. Well, tubes, really.

Here’s the inside of the plug. There is no wiring diagram here, but it matches that of the socket.

The earth tube is thicker than the rest, and there is a little earth sign by the larger cavity meant for it. The cable with 3 cores goes to the mains, and the cable with 2 cores goes to the pedal. If you have a metal-cased pedal, it is better to use a 3-core cable there too, for safety.

The wiring is then as follows, from the top:

  1. Earth – from one or both cables.
  2. Mains neutral.
  3. Pedal neutral.
  4. Mains and pedal line (live wire).

Good luck! 💥

8 thoughts on “Wiring Sew-Tric

  1. Great post ! Do you know wich type of of lightbulbs with bajonet fitting go into the lightfixture ? Keep upnthe good work !

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  2. Very helpful article, but your text doesn’t match the wiring diagram in the last picture. You’ve named the black wires as positive and the red wires as neutral. The way you’ve got it wired, it should read:
    Pin 1: earth
    Pin 2: mains neutral
    Pin 3: pedal neutral
    Pin 4: mains and pedal live

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  3. Hi Elena, wow what a wonderful blog site. Thanks for all that hard work and inspiration..
    I found an abandoned Sew-Tric machine and I’m trying to see if I can get it working. I’ve threaded it up but the bottom threader is stuck somehow. I’ve taken out the bottom threader (and now can’t put it back (doh!) and I can’t find any manuals online. I can’t see a date on the machine, but it’s a Sew-Tric Ltd Chiyoda. Series S 11?303 Class 1. RPM 6000. 20-60 Hz.
    I have a photo but not sure how to add it here.
    I would love some guidance as to where I can find a manual and then I can try and get it going.
    Thanks so much, Elaine

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    1. Hello Elaine, Sew-Tric is only the brand of the motor, it is different to the brand of the machine. The label that you quote belongs to the motor and lists its characteristics.
      You need to determine the make or at least the type of the machine itself, not the motor. The brand of the machine is usually written on the arm, but note again that the brand is not the same as the make – manufacturers used to produce machines for other brands (as is also the case today). But the brand would be a start.

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  4. I have 2 sewing machines with Sew Tric motors and after about 20 seconds the motors slow down and trips the power switches in the fuse board any idea what the problem is .. Thanks Fintan

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    1. Are you using electronic pedals with them? This happened to me. Other than that, the motor belts might be too tight overloading the motors. Then they start pulling too much power and overload the surge breaker.

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