Saturday, 31 October 2015

Repair of 1950s Singer motor

I met a fellow blogger the other day at Spotlight (Vogue pattern sale) and surprising number of amazing patterns left at only $5 each. Yes I know (bought 27), but I digress. She (thornberry.blogspot.com.au) told me to write something as I've been a bit slack recently.

So a few days later a lady from an FB group asked about repairing her older machines. Yes indeed there should be more information about this, so here is the most common electrical problem I've found with Singer motors: The wiring for the singerlight (that's what they were called by Singer) degrades and the wires touch, causing drama and blow fuses.

Here's the before picture (bit out of focus but still obvious what the problem is). This one is nowhere near as bad as I've seen. A lovely friend gave me a 201K23 for my birthday and the wiring was absolutely gone, and I mean no insulation left, wires totally touching each other at several places. This one would have been completely fine for decades, as the rubber insulation was completely intact, it was just the green outer that had gone. Pretty unsightly and looks dangerous, and I want to sell the machine (a 320K2). The rest of the power cable had already been replaced with the standard black.
Singer motor and light, connected by degraded flex
1. Remove the light. Prise off the end: This just pulls away with the lense still on. After this remove the bulb or it will get broken.
2. Unscrew the plate that's covering the light's mounting screw (already removed in the picture above) then remove the mounting. Put all screws back so you don't mix them up. That is, as soon as you remove the light, put the plate back.
3. Remove the motor screw then remove the motor from the machine and put the screw back in.

Now the motor and light have been removed as a unit. Put the machine out of the way until you're ready to put it all back on.

4. Disassemble the light.
4a Circlip 1. Just take a small screwdriver (jeweller's or the one for adjusting the bobbin) and unclip that circlip in the picture. This is one of two things holding the light fitting in one piece, there are no screws, just two clips.
4b Other clip is here:
Original was green, but snapped when I tried to remove it :-(
This clip is much harder to move. You don't have to remove the screw, but make sure you only turn it so the spring holds it less tightly. In the picture that means pushing the bit with the screw upwards. You need only a little turn, so the arms (already removed) can be pulled out. Pull them out. They will be pretty tight and they're sharp-ish, so try to grip them hard then pull away as you did the lense.
Now you can turn the clip and prise it off. Once off the light will separate into two.
Again, this is an after shot.
This is what the inside looks like. The wires (originally yellow and red) are soldered to those copper strips. Remove the copper strips with the wires attached.
and again
Unsolder the wires. This is a little tricky because you need dexterity holding, soldering and pulling at the same time. Make sure you remove all the solder, because the new wires have to go all the way through these holes.
The other ends are on the motor. Unscrew the long screws holding the wiring cover on. Remove the cover and the piece of cardboard and you should be looking at this.
well not quite: again this is an after shot
Unscrew what you need to and put the nuts and washers somewhere safe. The original wires are clamped and soldered to little circular washers. If you have these, use them. I don't.
Now you should have the original wires in your hand. You need to cut the replacement wire to the right size. Better to err on the larger side. Remove sufficient insulation and bare enough wire to wrap around the two posts on the motor.
Solder the new wire to the copper strips from the motor first, and before you install the other end in the motor, make sure you have both the light circlip and the white plastic motor wire clamp in place . The latter goes into the hole that the screw secures in the above picture (on the right). You don't want to leave either of these off.
Wires are now secure on the motor end
Put the white plastic back in its place and secure it with the screw. Reassemble the motor wiring cover.
All in place

With the cardboard insulation


Ready for the screws
Now the light end. Solder the copper wires to the copper contacts and insert them back into the light assembly. You might have to play with the switch a little to get them in. I used long nosed pliers. Don't bend them, you shouldn't need to force them at all.
Now it's just a matter of putting it together, replacing the circlip - you can push it over the lip and into the recess with your thumbs.
The next bit requires some force. Make sure you know which way to put the front light clip by lining it up on the machine. If you put it on backwards you'll get really upset. Put it on but not in exactly the finish position. It has to be off by a bit for you to reinsert the arms. Once you do this, turn the clip until it clicks into its groove and put the bulb and lense back.
If you screw this up, just have patience. I've done this a lot of times, and know it well. If you make a mistake, you'll probably not do the same thing again. It'd hard not to get angry if you do though :-).
Ready to go back on the machine
Doesn't it look nice? New plastic wiring should last a very long time indeed. I chose cord that has copper inside. Not sure if it makes a lot of difference but it shouldn't degrade over time.
Before putting it back on, check the brushes. These are small blocks of carbon whose purpose is to make electrical contact with the armature (of the rotor, rotating part in the middle of the motor).
Here's how to check the brushes. You're checking the size, and you can check how dirty the armature is too.
Remove the caps from the end of the motor - these are visible in the above picture. Take out the screw and you should be looking at this:
Exposed brushes
You can see the copper thing here. I pushed it up a little to make it clearer (which it didn't), but power is supplied from the wires on the right, which are soldered to the J shaped copper bit. The brass case is conductive and contains a metal spring pushing on the black carbon brush. The copper thing at the bottom is the motor's armature. This brush has already been checked and is fine. Check them every service and if less than half this length, replace them both. Don't take them out unless you have to: The ends are shaped as a curve by the armature and if put back differently you could easily lose power in the motor because the contact isn't as good.

No comments:

Post a Comment