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difficulty soldering dodgy wire

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difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 1:26 pm

Slightly off topic but I'm trying to repair an induction motor in a cheap bench grinder I bought several years ago. It has lain unused in it's box waiting for the workshop......

It power up but doesn't start, I have found a dodgy connection between one of the coils and the supply wiring. I'm struggling to solder the tail from the coil to the supply wire, the coil wire just will not tin*. I've cleaned the insulation varnish off with difficulty (and can get a connection with the Avo probe) as, obviously, the wires are very thin and break easily* but the wire underneath looks silver not copper coloured as I would have expected.

My last thought is to get a very small crimp connector to crimp on the coil wire and solder that to the big wire but I don't have any in stock?

Any suggestions from you experienced bench techs?

* I'm using 60/40 lead/tin solder and a soldering station set at 350ºC maybe I need some lead free?

** Which has happened a couple of times and I'm running out of wire to connect to :headbang:
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Re: difficulty soldering dodgy wire

Postby Eddy Deegan » Wed May 20, 2020 1:37 pm

Not my area of exertise but on occasion when repairing cables I've had success applying some fine-grained sandpaper to roughen a metal surface when solder doesn't want to cooperate.
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 1:40 pm

Yeah, that was my thought too but it doesn't seem to work in this case, neither does heavy duty flux (Fluxite). The solder just won't flow on the wire.....
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Re: difficulty soldering dodgy wire

Postby Eddy Deegan » Wed May 20, 2020 1:42 pm

Ahh, I'm afraid that exhausts my extensive knowledge on the subject. At least we tried every trick in the book, left no stone unturned and got everyone home safely ;)

I'm sure someone will be along presently who knows more.
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 1:44 pm

:D :thumbup:
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 1:47 pm

I've just thought, I wonder if it's aluminium wire? It's a cheap B&Q special so Chinese made waaay down to a price.

Will go and try to salvage some tiny connectors of an old computer circuit board of some kind to use as crimps......
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Re: difficulty soldering dodgy wire

Postby Folderol » Wed May 20, 2020 1:54 pm

It's probably some horrible nickel alloy.
I don't recommend a crimp. These things tend to have a lot of vibration and the weight of the crimp would result in fatiguing the wire right at the joint.

I solution I've used for similar jobs in the past, is to make a tiny twisted pigtail joint using a pair of tweezers then lay it close to the framework (but not touching) then smother with silicon sealant. The sealant will hold it in place, while also being vibration absorbing, and keeping moisture away from the joint.
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 2:05 pm

Vibration was a worry, and the original joints are soldered so you probably have the answer (i.e. not aluminium). I'll see what I can come up with. I was worried how to deal with re-fixing the wires, it's all in graded sleeves and laced together at present. Maybe a bit of solder wick for the flex part and loads of silicon will sort it out. Thanks Foldy. :thumbup:
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Re: difficulty soldering dodgy wire

Postby James Perrett » Wed May 20, 2020 2:29 pm

At one point I had some solder that was supposed to work for aluminium called Alusol. I think you may still be able to buy it from CPC or Farnell but it isn't cheap.
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Re: difficulty soldering dodgy wire

Postby Wonks » Wed May 20, 2020 2:35 pm

James Perrett wrote:At one point I had some solder that was supposed to work for aluminium called Alusol.
Don't confuse it with haemorrhoid cream. ;)
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 2:40 pm

"Preparation H"?.......
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 4:17 pm

Thanks guys, a little perseverance and some fiddly sh1t and it not only works, it sounds sweet as a nut, and, it passed a PAT.... er... test..... :thumbup:
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Re: difficulty soldering dodgy wire

Postby Martin Walker » Wed May 20, 2020 4:59 pm

The PATer of tiny nuts?

I'm confused now...


Martin
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Re: difficulty soldering dodgy wire

Postby Wonks » Wed May 20, 2020 5:33 pm

Sam Spoons wrote:"Preparation H"?.......
Image
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Re: difficulty soldering dodgy wire

Postby Sam Spoons » Wed May 20, 2020 5:34 pm

Martin Walker wrote:The PATer of tiny nuts?

I'm confused now...


Martin

There were quite a few tiny nuts, and they did patter when I dropped them on my (newly painted) workshop floor yes. :D

Yes, Wonky, I know, I'm old too you know ;)
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