[R-390] Mechanical Filter Repair

[David C. Hallam]

Green color insulation on magnet wire quite often, but not always, indicates
a urethane insulation which is solderable.

When you burn off insulation, you need to remove the oxidation created
before soldering. A few strokes with a fine emory cloth will do the job.

Magnet wire is already annealed.  That's why it can be wound in coils
without springing out.  The lack of spring back is an important attribute of
magnet wire that every manufacturer measures.

Soldering causes some alloying of the copper with the tin in the solder and
the heat causes some grain growth at the point of application.  The finer
the wire, the more important these considerations become.

David
KC2JD/4

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Buzz
> Sent: Thursday, June 14, 2007 1:18 PM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] Mechanical Filter Repair
>
>
>
> Members,
>
> I have found that magnet wire with green insulation will burn off
> when tinned.
>
> When I have used a lighter to burn of insulation I find that the
> wire anneals
> and is difficult to solder.
>
> Soldered wire is subject to breakage at the end of the tinning
> because that is a
> concentration of stress point hence the use of strain reliefs or potted
> connectors.
>
> For tacking wires locktite makes several products available at electronic
> stores.
>
> Buzz
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