Rewiring Vintage Sewing Machines

We are going to cover the basics of rewiring vintage sewing machines, rewiring duplex plugs, and rewiring Singer 3 connection terminal block. The following instructions are from Paul. He has the expertise to help with all of your vintage sewing machine repair needs. The table of contents below will help you get to the portion of the rewiring that you need

Rewiring Vintage Sewing Machines

My goal today is to show others how to replace the rotten wiring we have all run across when we get new to us machines. I want to demonstrate enough about the circuit that anyone reading will feel comfortable with their ability to pick up the parts and wire and within a couple of hours have a safely wired fully functional sewing machine.

My plan is to use as much common language and plain talk as possible, I want to keep my explanations as understandable, safe, and simple as possible. My analogies may not reflect the physics of electrical theory. But they will reflect how electricity works, how it can be controlled.

I do not intend to try to teach an electrical class within the confines of a blog post. We will be using a standard 120-volt generic sewing machine as our practice dummy. It starts out very basic and as we succeed in understanding each step, we will add more steps and eventually rewire a complete machine with a controller and on/off power switches and light switch circuits. Our practice dummy doesn’t have any extra whistles and bells like low-voltage lights or multi-speed motors. Those just add confusion to the circuit that I am going to show you. Maybe we can do a more advanced class and go into more detail at a later date.

Basic Sewing Machine Wiring Circuits

Sewing machine wiring circuits are all basically the same design with the idea being to create an electrical path from the source, (the wall outlet) to the power switch,(if available) then it will branch off into two separate circuits. One circuit will go to the light if available and the other will go to the speed controller for the motor.

Here is where my means of explaining the manner in which electricity travels differs from the physics of electricity but it follows the flow of the energy that is carried in the electricity and it is easier to understand the concept at a novice level.

We are going to assume that the source wiring is correct and we will proceed under that assumption. Also, we are going to assume that the outlet is polarized and grounded. Older-style outlets and plug-ins were not polarized or grounded and they only had two slots in the outlet or two blades on the plug-in.

Early Types of Wiring Circuits

On these early types of circuits, the plugs and slots were the same size, and electrically on a standard 120v circuit, they were interchangeable. They were at the time considered adequately safe for use even though from time to time a person could receive a shock if the circumstances were not perfect. As electrical safety evolved so did the standard outlets and plug-ins.

The second-generation design consisted of a wider slot on one side of the outlet and a wider blade on the plugin to match. This was done in order to assure the two wires from the electrical panel to the outlet would always be polarized in their function of the flow of electricity. The wide blade would always be the NEUTRAL (white) wire in the circuit, while the narrow blade would be the LINE (black) wire. A copper or brass terminal for the LINE side and a silver terminal for the NEUTRAL side would also identify all of the fixtures (outlets and light sockets).

Current Circuits

In the current evolution, a third wire was added as a dedicated ground wire identified as a green wire or a bare wire,(no insulation). The third connection is identified by green terminals and its fixture connections or slot is below the original two blades and it is round or (U) shaped.

It is important to acknowledge the changes in the electrical specifications and to understand the purpose of the changes. It is also important to realize that those changes have no relevance as far as increased safety for household appliances not intended to be used in damp wet conditions.

Using Extension Cords For Rewiring Vintage Sewing Machines

Light-duty extension cord sets are still available with only the two-blade outlets and plugins. The outlets and the plug-ins are not the only parts of the circuit being identified as polarized. The insulation covering the wire is also identified. Sometimes the identifier will be a white or gray stripe running parallel to the wire. This stripe is also called a tracer. Ridges molded into the insulation during the manufacturing process may also identify it.

The important thing to remember when using a lamp cord or extension cord to repair or replace faulty wiring is simply, wide blade or slot, tracer stripe, and ribbing on the outside of the cord are all Identifiers for the NEUTRAL or N ( white wire). With 120v circuits, it is not uncommon for N to be referred to as L2. No tracers, or ribbing on the insulation and narrow blade or slot designates it as LINE or L1 (black wire) in the circuit. Now that we know what the wires are, it’s time to discuss what they do.

L1 in Rewiring Vintage Sewing Machines

In the simplest possible terms basically, the L1 is the power wire that brings electricity from the source to the OFF-ON switch if the machine is equipped with one. When the switch is in the ON position the electricity passes through the switch and branches off to the motor controller, and to the switch for the light. When it is off it stops all the electricity to the machine. The second switch when in the on position passes the electricity to the light if the machine has a light. The motor controller is a variable switch that doesn’t pass all the available energy thru to the motor until it is pushed to its max limit. That is why the motor will run slow when you barely push the controller and at full speed when you press it hard. That is all L1 does. It provides a path for the electricity that is carrying the energy needed to make the light come on, and give the controller (foot or knee pedal)the energy it needs to pass along to the motor.

L2 in Rewiring Vintage Sewing Machines

After the electricity hands off the energy to the motor and the light, It needs to return to the source where the cycle starts all over again. This is what the N or L2 wire does. It provides a path away from the light and the motor back to the source. L2 should not be switched, It doesn’t damage anything if it is and the circuit will turn off, the preferred method is to leave Neutrals or L2 un-switched and do all the switching with L1. If you get crossed up and L1 gets switched to L2 you will trip breakers, blow fuses and may even see some sparks and smoke. Understanding this method of identifying the wires will make it much easier to keep the wires from getting all crossed up when you are re-wiring any projects, even sewing machines.

Rewiring Vintage Sewing Machines

Ok now that we are armed with this information. Are you ready to re-wire our test dummy sewing machine? I think we are and if we have problems then we can refer back to the paragraph above and work through the glitch. It may seem a little overwhelming at first but you can sketch out your own schematics to help you keep from getting lost and confused. There are no brownie points for doing it all out of memory. As long as you can understand your own drawings who cares how rudimentary they are. I have even used multiple colors to help me keep track of the different wires in the circuit. And most of my drawings only make sense to me.

So let’s give it a try, We start at the wall outlet or power source. We need a power cord with a plug-in that matches the source. We do not plug anything into the source until we are completely finished with our wiring project.

Connecting L1

Now we need to connect the L1 side of the power cord to one side of the Off- On switch. On the other side of the Off-On switch we need to connect one of the wires from the controller, and one of the wires from the light switch. The other side of the light switch gets connected to the light fixture. Now we go back to the controller, the second wire from the controller will get connected to one of the motor wires. All of this wiring is from the L1 side of the circuit.

Connections are made in a variety of fashions, They can be wire-nuts twisted over the bare wires to tie the ends all together. They may be screw terminals, in which case wires are held together by tightening down a screw and pinching the bare ends together.

They may even be crimp-on connectors that are squeezed into the ends of the wires using special pliers.

You may be soldered together and insulated to keep them from grounding out or shorting together.

Regardless of the type of connections used, the important thing is the bare ends must be covered to protect from getting shocked or to prevent L1 and L2 from coming into contact with each other or grounding against the side of the machine.

Connecting L2

We are now ready to connect the L2 side of the circuit. Starting at our power cord the L2 side of the cord needs to be connected to the unused wire from the motor and the unused wire from the light fixture. This should leave no unconnected wires in our circuit and we should be ready to plug in our power cord. Turn the switches both to the Off position. Plug the cord into the wall outlet and nothing should happen. Turn the power switch to the on position. Nothing should happen here either. Now press on the motor controller and the motor should run at speeds relative to the position of the controller. Release the controller and switch the light switch to the On position. You should have light if the bulb and the fixture is good. If you have light, turn the power switch back to off and your light should go off even if the light switch is in the On position. If you have achieved all the functions as described. You are successful and your machine is fully rewired and ready to serve for many years of happy sewing.

Rewiring Vintage Sewing Machine Duplex Receptacle

Now we are going to work specifically on one of the most common wiring styles found in a multitude of various manufacturers of sewing machines. Using an electrical fixture very much like a duplex receptacle and two standard two-blade 120v plugins make it one of the most versatile methods which can be used on any machine in need of a control system.

Not A Household Duplex Outlet

At the time of the writing of this post, we have re-wired dozens of machines that had incorporated this technique but I have never found a true name for this method. I typically refer to it as the Duplex system because it appears on the outside to be a 120v duplex receptacle with the words MOTOR over one plug-in receptacle and LIGHT over the other. However, that is where the similarity stops. Once the cover is removed, the wiring is nothing like a standard 120v outlet.

Above I explained all about the Line 1 and the Neutral or Line 2 wiring identifiers and the importance of using the proper wires in order to keep the circuit from becoming a confusing mess. It will be equally important to be as meticulous with the wiring of this system as it was with the previous system as it will ultimately prove to be with any wiring project. If you find the terminology confusing please don’t give up. Instead, refer above and it will all be explained. If that doesn’t work in your favor we welcome comments and questions and enjoy helping where we can, so you can directly contact us and we will get back to you as soon as possible.

Where are these plugs found?

This type of system is typically found in the portable tabletop models of any given manufacturer but it is not exclusive to the portables. It was also used on cabinet models as well. The only difference between the two has to do with the space requirements versus the ability to substitute some of the components with local hardware parts. For simplicity’s sake, we are going to approach this from the direction of a portable machine with the understanding that it can be adapted to the cabinet models simply by making the wires longer.

Ok all that being said and done let’s get started on our latest new to us treasure machine. Of course, it’s portable and when we pulled the lid off we noticed crumbling insulation on every wire we touch. As we look it over we see that the wiring from the motor and the light is nothing more than a pair of short (pigtails) wires with a standard two-blade plug-in on the end. The two plug-ins match up with labels on the face of the duplex-looking electrical box. One label is for the MOTOR and the other is for the LIGHT. The duplex is mounted by a single screw behind the handwheel in the space that was originally intended to house the various attachments and implements of sewing destruction. IE pins/needle/bobbins /seam rippers/scissors etc. Since we refer to the length as the side of a box and the narrow part as the front and back end, we can see a pair of wires exiting each end of the duplex. One of these pairs of wires will go directly to the motor controller, usually a foot pedal. The other pair of wires will go directly to the 120v source outlet on the wall. Since we are going to have to replace almost all the wiring we will start by unplugging the two pigtails from the duplex and removing the screw in the center of the duplex thus releasing it from the wooden box the machine is in. Oh yes, this reminds me, this style was also used in the plastic carry cases exactly the same layout excluding the mount screw. Instead, plastic pressure tabs were molded into the bottom of the case to hold the duplex solidly in place. The duplex is still removable. After we have the duplex out we can turn it over so we can see the bottom of the duplex. It has a HEAVY cardboard piece held in place by two press rivets. The rivets are easily pulled out if you can get a pair of pliers to grip the head or if you can get the jaws of a pair of wire cutters on either side of the head and pry up against the head of the rivet pulling the rivet from the Bakelite duplex cover. I have found that I like to use a pair of jewelers wire snips. They are very flat wire cutters and can be found in any craft store that carries beading or jewelry supplies and wire. They work great for pulling small nails and staples also. Now that we have the rivets out we can remove the cardboard to reveal the inside of the duplex. Pay close attention to the brass strips inside the duplex. If they come out during the wiring process its ok but they have to go back in exactly as they come out or when we are done we won’t get a connection from the wiring to the plug-in pigtails when we plug the motor and light back in. Some of these strips do not come out but most of them are free floating so to speak and they will easily move around and fall out. As we look at the brass strips we will see how the wires from each end are connected. Some are screw type terminals with the wire mounting under a screw. These are easy to deal with. Some of them are soldered to the wires coming from the respective components (foot pedal and power cord). Not as easy but still possible to manage with a minimum amount of soldering skill.

Now before we proceed there are a couple of ideas I would like to share with you. First of all if the duplex is the type that will need the wires soldered back onto it and you absolutely do not want to solder, there is a second alternative to solve the problem and bring the new old girl back to the prime of her life, you can follow the wiring diagram from our earlier post using shrink tubing and crimp connectors. Slide the shrink tube on the wire make the connection and slide the shrink tube back over the connection and heat shrink it into place. These connections can easily be manipulated into living under the machine bed out of the way of the running gears and survive happily ever after. Remember not all of these old machines came equipped with a power switch because they were portable and were expected to be unplugged and stored away. So just omit the first switch from the circuit and proceed onward. Secondly, when I rewire these old machines sometimes the old two blade plug is too far gone to use again and must be replaced. We could go to the hardware and get new ends and about 10ft of wire and rewire it all the way through. Or we can go to a local for the cheap store and buy 3) 6ft indoor extension cords cut the plugs off of 2 of them the length we need for the pigtails. Cut the receptacle end off of 1) making a long pigtail to be used for the power cord to the wall outlet. Cut the receptacle end off of 1) of the left over pieces from the short pigtails to be used as the cord from the duplex to the foot pedal. Over all, it may cost a couple bucks more but we didn’t have to hassle wiring the plug-ins on and our wiring now has the molded plugs for a more finished appearance. Just an option it’s your choice so it will be right for you regardless of the decision. There is one downfall involved with replacing the two blade plug-in. The new replacement plug-ins will probably have the wide Neutral blade and it may not fit into the existing slot of the duplex. When I run into this situation I take a file to the brass blade and after a few strokes, the blade fits the slot.

Now that we have our duplex removed from the machine and have disconnected the old wiring from the brass strips. We are ready to start reversing the process and start connecting our new wire. We are going to start with the power wire from the source and reconnect it to the duplex. We need to be sure when we start that we have our duplex facing the right direction so when we finish we will have it wired correctly and the machine will run like a dream. So we set our duplex on the table with the labels up so we can read them. The LIGHT end of the duplex should be closest to us or lowest in line from the edge of the table. Now we roll it over so the labels are now face down on the table. We will stay true to form and keep our duplex properly polarized. Because our duplex is facing away from us instead of towards us the Line (L1) is on the left side and the Neutral (L2) will be on the right. Before we start rewiring the duplex we need to make sure there is a connection from the L2 point of contact of the LIGHT receptacle to the L2 point of contact of the MOTOR receptacle. Sometimes it will be an inherent connection by design of the brass strip. BUT not always. Sometimes it will require a jumper wire between the two so the connection will be made. There must not be a connection between the L1 MOTOR receptacle point of contact to the L1 LIGHT receptacle point of contact. After visually confirming the points of contact we are now ready to start connecting the wires to the duplex. We are going to start with the L1 wire from the long pigtail power wire we made for the wall receptacle and the L1 wire we prepared for the motor controller. Both of these wires need to be connected to the L1 point of contact of the LIGHT receptacle. The L2 wire from the motor controller needs to be connected to the L1 point of contact on the MOTOR receptacle. The L2 wire from the long pigtail power wire needs to be connected to the L2 point of contact on the LIGHT receptacle. We are done with the wiring of the duplex and ready to reattach the cardboard back and push rivets and fasten it back into the case via the screw or the plastic locks.

The short pigtails we prepared for the motor and the light are ready to be wired to the motor and light respectively. By carefully cutting the old wires about 1 1/2 inch from the motor and the light we can strip the insulation off of ½ inch of the wires and slide shrink tubes onto the insulation before we solder or crimp connect the new pigtails to the existing wires. After the connections are made the shrink tube can be slid down over the connection and heat shrank into position. Once this is finished we are done with the new wiring of the old beauty and she is ready to try out her new wings. Plug the motor plug into the MOTOR receptacle and the light plug into the LIGHT receptacle. Plug the new power wire into the wall outlet and turn on the switch for the light. It should light up and we will be ready to press down the motor controller. The motor should run in relationship to the position of the controller. Push harder it should run faster until max limit of the controller is reached, at which time the motor should be at full speed. This concludes our test and we are ready to begin a new Life of projects for our old machine.

Rewiring a Singer Three Connection Terminal Block

Singer used this type of terminal block set up for a vast number of its machines, Variations were found on everything from the tiny 221 Featherweight to the 400 series family. Including the 66, 99,201,301,306,319, and of course the 15 series. We will explain the different ways the machines were wired using the basic design and how it evolved through the years.

I usually don’t like to get brand specific when we are talking about general maintenance and or cleaning up the machines to bring them back into smooth running order. But this time we need to delve into the known –unknown and explain a little about the specific wiring of the Singer terminal blocks. Notice the plural, yes they used the same blocks above the motor mount for a long time and for a variety of machines. The fun part is they used the same terminals on the block itself for the motor and the light but they changed and evolved the points of connection for the power and for the controller. Because of this factor, it can look very confusing when the diagrams don’t reflect the visible change on the machine itself. So to help to eliminate the confusion I am going to try to explain why they look different but electrically function the same way.

We are going to begin at the terminal block on the back of the machine without the power plug plugged into it. The block is held in place by a single screw above the three brass pins of the terminal block. By removing the screw the terminal block is freed from the machine and can be turned over to gain access to the wires and the thumb nuts which secure the wires to each individual terminal. Old wires will harden and can make turning this over difficult to do. If the wires are that hardened with age and use, it is time to replace them anyway. From the back side we can see terminal designation numbers and in some cases, the numbers are still color coded as well. Terminal #1 was originally YELLOW in color and the necessary wires were YELLOW also. Terminal #2 was BLACK and all the wires connected were BLACK and terminal #3 was RED with only RED wires attached. All that was needed was to match the wire colors with the proper color terminal and the machine practically wired itself. Although it is possible to acquire replacement wire of the proper color it isn’t always feasible to do when most replacement parts are going to come shipped with black wire leads and replacement wire for the controller or the power cord will be from hardware stores typical inventory, commonly black, brown, or white. Colored tape or number tags/stickers can be used to designate wires if desired. Paint can fade or crack away but the number will always be there. And with that thought in mind, we will only be using the # designations and not the color as a guide. I will still use L1-L2 to keep our wires from getting crossed up.

We are going to begin by wiring our motor and our light to the terminal block. Starting with our L1 (switched wire) for the LIGHT we will connect it to terminal #1. Our L1 wire from the MOTOR will always go on terminal #2. Our L2 wire from the LIGHT and the MOTOR will always go together on terminal #3. This part of the wiring doesn’t ever change it will always be wired this way.

When our MOTOR CONTROLLER is not wired to the power cord plug-in, and if it does not have a dedicated plug-in of its own then it must be wired to the back of the terminal block. To do this one of our wires from the CONTROLLER will become L1 and it will be connected to terminal #1 with the L1 from the LIGHT. The second wire from CONTROLLER will get connected to terminal #2 with the L1 wire from the motor. This is all of the wiring needed at the back of the terminal block. With this configuration, our power cord is simply a two wire plug-in with L1 going to the plug-in socket that matches terminal post #1 and L2 going to the plug–in the socket that matches terminal post #3. The downfall of this variation was simply the controller was permanently attached to the back of the terminal block and could not be removed for travel or storage.

The second variation of the wiring was to remove the controller wires from the terminals of the block and add them to the power plug. The L1 of the controller is still making the connection with L1 from the power plug. Only now it is on the plug-in side of the terminal block. The second wire from the controller is still making contact with the L1 for the motor because it is now wired to the #2 terminal connector on the power plug side of the connection. This configuration allows for the controller and the power plug to be removed for transport or storage.

The final variation of this basic wiring system also came with some physical changes. The terminal block no longer mounted to the motor mount. Instead, it was changed into a modular socket that was incorporated into the pillar of the machine. The terminals were still the same and the wiring diagram didn’t change. The terminal connections did however change. The connections are no longer thumbscrews instead they are soldered connections or they are soldered pigtail extensions and the actual connections are either wire nuts or push to lock connectors, Some of these machines have even deleted the center pin terminal from the modular socket. Even so, they still use the three wire terminal plug-in power cord and a dedicated terminal socket added to the body of the machine for the foot controller. The socket would match a two wire plug-in attached to the controller. The wires from the mounted socket would, in turn, find their way back to the terminal block #1 and #2 exactly like the first variation with the difference being now the controller has the capability of being unplugged from the machine for storage or transport. All of these variations use the same basic wiring schematics but they change the point of contact for the motor controller.

I hope some of you got a laugh from my struggles to explain the how’s and why’s of the Singer 3 terminal wiring system. I hope in some small fashion it helps cut through some of the confusion when looking at different Vintage Singer sewing machines and trying to rewire them.

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