Little help wiring an old sewing machine plug, please?

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Old 09-05-18, 11:56 AM
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Question Little help wiring an old sewing machine plug, please?

Hello, I would need a little help with an electrical issue and I think the users of this forum may well be the right people to give me a hand.

I had this old "Hanseatic" sewing machine that one day have a short circuit: it made a spark that scorched the plug a little and stopped. I took the plug appart and saw that the wires were loose and had apparently made contact, so all I needed was to get them out, clean a little ash, and put them back in place more firmly... but, fool of me, I lost the paper where I wrote the order in wich the wires are connected, and I have zero knowledge in electricity, so I'll describe the plug (picture ahead) and wires, see if someone can help me out.

Is the plug that connects to the sewing machine from both the control pedal and the wall socket, so I have six wires (three from each: black red and green) and the plug have four pins, as the picture show, in wich I can read, left to wright and top to bottom: "N", "E", "P" and "RP". But that letters... I'm not sure, but maybe are from german words. So... any ideas?

Thanks for your time
 
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Old 09-05-18, 12:21 PM
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I think we need some more information as there are 6 wires and only 4 terminals pictured. Can you show us the whole cord assembly including the wall plug, pedal and machine?

I see it is a German machine, however is it made for use on the European electrical system or North American electrical system?
 
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Old 09-05-18, 06:03 PM
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Thanks for answering. The machine is made for european system, and the six wires were in those four pins, but I'll show you the whole assembly.

First picture shows how the wall socket and the pedal both connect to the four pinned plug; I included the cover of the plug with two holes to show that these are for the two thick wires, one from the wall socket and the other from the pedal.

Second picture is the wall socket, opened, so you can see that the green wire is ground. Usually is yellow around here but this is so old...

Third picture show the machine, were the plug goes. What appears to be the continuation of the same six wires, in two tubes, goes on from there into the machine: one to the motor, but the other is hard to see.

In the pictures is not clear, but now that I looked again I can see how they go, up to bottom: in the first pin there is one green and one red, but each from a different tube; the second is the other red; third the two black ones and fourth the other green... really messy...

OK sorry to bother you, I think my brother figured that out while I was writing this. Or maybe we just figured out most of it... I'm sending it anyway, and tomorrow I'll explain how we think the wires go, because this side of the ocean is pretty late.

Thank you again
 
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Last edited by raulm60; 09-05-18 at 06:23 PM.
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Old 09-05-18, 07:37 PM
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I am pretty sure that pedal just contains some sort of variable resistor like rheostat.

4 pins on that connector should consist of following.

Neutral (That European plug is not polarized, so neutral can be considered just a shared live wire.)
Power to Light (one of the line directly from the plug)
Power to Motor (feed from the pedal)
Ground (earth)

One of the wire (either black or red) will be wired together with one of the wire from the plug to the pin supplying power to the light.
Ground (green wire) will be connected together.

You will have to find out which is which by testing with multi-meter or following the line in the sewing machine.

Ground can be found if testing continuity to the chassis.
Power to light and neutral can be found can be found by testing continuity to the bulb socket.
The pin you did not get continuity to neither of 2 contacts on the bulb socket will be power to the motor.
Measure resistance between this power to the motor pin and one of the pins going to the bulb (with bulb removed). The one you get some low resistance value will be the neutral and the one you get open circuit (very high resistance) will be power to the light.

It will be wired something like below.
 
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Old 09-06-18, 11:21 AM
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Wow, thanks a lot, I see that is much clearer when you draw it, so I'll try too, but let's start from the begining.

As I told you my brother thought he has it figured it out, but now we are not entirely sure.
The missing thing in your draw is that there are three wires from the foot pedal to the female conector, not just two.

We belive the letters from the female conector stands for Earth, Regulated Power (for the motor, from the pedal), Neutral and Power (for the light). Extrangely enough, the male conector is labeled diferently: only the counterparts for RP and P are marked as "M" and "L" respectively: should be light and motor, wich makes sense.

But here is the thing, the actual configuration of the wires from the male conector is like this:
 
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Old 09-06-18, 11:32 AM
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My draw sure is worse but I think is understandable. I included the labels of the female conector in brackets.

To me, the extrange thing is the red wire coming out from "E" pin. I disasembled both the plug and the pedal, and the green cables both go to ground, so I would attach them to the E pin; then the black wires must be neutral, so goes in N, and the red ones would go to RP (from the pedal) and P (from the plug).

but why are to diferent colored wires coming out from the male conector? somebody messed with this thing or what? I mean other than me, of course :P... is second hand, in fact a gift, but worked perfectly until a day that made that spark the instant I plugged it.

But in any case we got a multimeter, so I'll try to follow your instructions, again thanks a lot.

Regards
 
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Old 09-06-18, 01:26 PM
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We need to know what the pins are on the machine. I see your drawing but you can't have grounds on live pins so that may be a mistake. It looks like you may be able to take the receptacle off the machine and look at the wiring on the back. There should be a common pin that goes to the motor and the light, There should also be a common pin for ground where all green wires should connect.

If that wiring is indeed how it's wired..... it's wrong. The red and green from the light are shown reversed.

Based on your pin labeling.... this is what you should have....
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Old 09-06-18, 03:29 PM
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But here is the thing, the actual configuration of the wires from the male conector is like this:
Checking with multimeter is the best solution. Green should be used as ground, but the person wired it may have used it for other purpose.

Green wire from the pedal should be ground as well, but it is best to confirm that with a multimeter.

I did not draw the diagram. I just found it on-line. It was for Brother sewing machine.
 
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Old 09-10-18, 08:22 AM
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Wired up and runing! I tested and it works nice.

It took me a while cause apart from buying a new multimeter (old one broken) and actually learn how is used, I also doubled checked by taking apart some other machine pieces and see where the wires ended. I also opened the pedal and saw how rehostat works. So I think I learned a little bit out of it (electric circuits have always been a mystery to me).

I could confirm that the green and red wires to the light from the male connector were incorrectly colored (red wire was used for earth and green for power). But all the rest was as in Pjmax diagram.

Thanks to the kind people of this forum. Best regards.
 
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Old 09-10-18, 12:38 PM
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Good thing you confirmed. If you wired red to live wire as it is, you could have made whole sewing machine live and electrocute.

It is good practice to always double check and not just rely on wire colors.
 
 

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