questions about rewire for a 15-91
 

I'm ready to start replacing the old wire on my 15-91 and I have a few questions. The new wire has printing on one side and I assume that is the (+) side. But the old wire doesn't have anything to help me decide about the positive and negative side. The plug is the old type where the prongs are the same width.

I got a wiring diagram from sew-classic but it doesn't show + and - either. So, can someone help me with a diagram showing + and - for wiring this 15-91. I do plan on removing the old wire and replacing the new wire one wire at a time. I just don't want to hook it up wrong and burn out my motor or something. I'm thinking that + and - does matter for the motor and the light even though the foot controller is just a switch and doesn't matter. Thanks to Joe, I learned that.

I'm still a little nervous about electricity..... very high respect for it but if I don't know what I'm doing...... ??? Fireworks are pretty but not when it's my sewing machine.... if you know what I mean.

Jean,

Are you going to rewire the motor, the connector block, just replace the cords, or all of them?

The motor has red and black wires inside, I matched that when I did mine.
The connector block is color coded. Basically just match the new to the old.
The cord sets are already wired, just attach the controller, it's not polarized.

Here is two places to read:
{ http://www.quiltingboard.com/vintage...r-t205360.html }
{ http://vssmb.blogspot.com/search/label/rewiring }

Sometimes the side of the wire with the printing is the + side. Sometimes the wire has ribs on it as well. It drives me crazy trying to figure it out cos there seems to be no hard and fast rule of which method of marking means what.

Joe

technically, the motor type is ac/dc and its windings are not polarized. AC plugs weren't polarized then either. The color markings are to aid in assy. Neither leg should be making any contact with metal you can check your work when fone by having it unplugged from the wall, use a continuity checker and verify there is continuity through the motor wirin but none from either leg to the metal housing.

Thanks, Joe. I'm just going to replace the wire. I took the machine out of the cabinet and marked the ends of the wires.... which go to 1 which go to 2, etc. The old wire started crumbling and exposing the wire.... that means it needs to be replaced. So, I'll read what you suggest and get back with you. We're having a pretty bad storm going through right now so we may loose power. I sure hope not but I may be able to check things out.... I may not. I do have the 'puter unplugged right now. I don't want to fry the 'puter.

Thanks OSS. I do have a continuity tester. So, if I understand you correctly, if I've wired it correctly, I should get conductivity when I touch the wire going to and from the motor, to and from the foot controller and to and from the light. Is that correct?

Basically, if I follow the wires that are there and assign the 1st one as positive I should be okay, correct? I just need to be careful which # on the 3-pt plug is to be + and which is to be -. But if I assign the 1st one to be negative, that's okay, too? ... as long as I keep track of the +'s and -'s to assign to the other points?

youll get continuity thru the motor. the contoller may not show continuity until its almost fully depressed. The lite wiring will show cont only with a good bulb and the switch on. And it may not be 0 resistance because the bulb filament has a small amount of tesistance. I test my reworked motors by leaving their cord long putting a temp plug on them do I can check them with an old style line wiring receptacle block. Also helps to plug into a gfci outlet even tho its not a grounded 3 prong plug, because theyLl trip faster

not to worry you needlessly, but you are safer to plug it in with your left hand in your pocket so as to not provide a return path thru your body.

What about your feet on the ground?? Okay, I totally understand the left hand in the pocket..... scary.... I know just enough to make me dangerous.

rubber soled shoes, dry floor.

I need to keep track of this thread because I think my new-to-me 15-91 needs some electrical work too. Thanks for all the info. even though I was not the first to ask.

KLO,

Very likely. Back in the 30s, 40s, 50s, they used aluminum wiring covered with latex insulation. Aluminum is an excellent conductor for electricity but it swells and shrinks due to heat. This breaks down the seal for the insulation, and can cause screw connections to loosen. A big cause of house fires.
Aluminum wiring is also prone to corrosion.
The latex insulation ( same stuff as surgical gloves ) has a limited life time and eventually deteriorates. Then it can turn gooey and melt .... ick, or dry out and crumble away. Sometimes, as in my 15-91, at the same time.

So any machine made from those eras needs a through electrical inspection and evaluation before being plugged in.
The results of bad wiring can be catastrophic at the worst, and exhilarating in a bad way at the least.

Joe

Thanks again. I looked at the sites you posted. I'm going to have to go at this slowly. ... and probably go to the hardware and the electrical supply. The wire to the foot pedal is the one that is crumbling badly. The others still look pretty good. I suppose I need to replace it all..... gotta work up my courage.

Along with all great advice, tutorials and information take photo's, make notes, and work slowly and you'll quickly have the bad wiring replaced. If you think of the operation as replacing old wire with good new wire it sort of puts things in perspective. A healthy fear or respect of electrical work is essential. Only the foolhardy plug in their 15-91's without first examining the wiring for safety.

Jon

Jean,

If the only wire that's bad is the foot controller wire, then it's an easy fix. Just pay attention to where the wires are connected and put the new ones where the old ones were. It's that easy.

Of course I could go on to say that I make the little rings on the machine end from the cord wire, and solder them so the screws hold good, or I could say I solder the connections on the controller ends for good strong connections too, but I've said that before so it would be repetitive ...... oops, I did it again ..... :)

Joe

Jean, here's some information about electricity:
http://www.archaicarcane.com/love-be...ewing-machine/

When I wire a motor, I use regular wire, singles stranded, so there's no deciding which is positive and which is negative.