On Mon, 25 Dec 2006 02:31:40 GMT, larry wrote:

mm wrote:

AIUI, when soldering to an enameled wire, there is no need to remove
the enamel first. It just burns up and disappears when one is
applying the solder. Is that true?

Otherwise, are there any tricks to repairing a small transformer**
such as used to power an audio device such as a clock radio from
110VAC: I take the cover off and the first layer of "tape" and if
there is only a half inch of wire going to the priamary winding, and
if when I try to solder to it, it breaks off just as it goes into the
winding, under other stuff, I haven't been able to fix them in the
past. But maybe there is a trick I don't know.

**The one in question today has 3 secondary windings,
green-yellow-green, red-red, and blue-blue. Does that indicate what
the output voltages should be?

It's 1 3/4 x 1 3/4 x 1 1/2 inch and it runs a high-quality Panasonic,
clock-radio, sterero cassette player/recorder. Model 680-3870


overheating enamel insulated magnet wire never makes it
solderable. Just destroys it's insulating qualities. On
fine wire, use a thumbs worth of fine steel wool. Poke the
enameled wire into it, squeeze lightly and pull the wire
out. Repeat (rotate wire a little) until the end is shinny
copper. Practice with different sizes until you get the
squeeze pressure down, before taking on the real repair.

There is magnet wire manufactured with synthetic insulation,
that can be heated and soldered in one step. Some trade
names were Nyleze, Soldereze etc. These are almost always
bright color insulations, red, green, blue, and yellow are
common. If you touch a hot soldering iron to it, the
insulation will form small beads that will move along the
wire, away from the iron tip.

One caution, a lot of shop appliance motors (drills, hedge
trimmers, weed eaters) use insulated ALUMINUM magnet wire!
No matter how well you remove the enamel, the wire looks
"tinned" and just won't solder. You will also see only
small brass crimps used to connect to this stuff.

Thanks for all the valuable, interesting information. I'll remember
it.

Many manufacturers offer reasonably priced replacement
transformers. I also wonder why you have so many failures?

Me? In the last 10 years or more, I have only had this one failure of
a transformer. I have failures in general because I look for them. I
pick up broken things to fix them. They are usually broken before I
get them. Often my friends save them for me, or I get them out of the
trash or at yard sales. It's a hobby. Often I give them away after
they are fixed, or give them to Goodwill.

One time in NY, on my to the car on a Sunday I found a tv in the
trash. I had a date -- we went to the zoo and to dinner -- but I
looked forward to working on the tv when I got home. Sadly, it worked
fine.

I have on occasion "unwound" a bad (internal short)
transformer, removing the "lams", counted the turns. Then
gauged the wire sizes and rewound the coil and relaminated
the stack. It's getting difficult to find small quantities
of numbered magnet wire, the papers, and electrical varnish
these days. The only high tech tools? Micrometer, wire
standards, and an oven. Kitchen type works fine if the
"boss" isn't home ;-)

Interesting.

When I was about 12 to 14 I unwound a broken motor from an erector
set. We couldn't afford an erector set with an electric motor, only
the one with the spring motor, but a friend gave me his broken
electric one. I unwound the enameled wire and found that it was
broken at every 2nd corner or maybe every turn. I scratched the
enamel off of both ends of every piece, hooked them together, and
wrapped it up again. Then I made the mistake of wrapping it in
electric tape instead of plain cloth. It worked but as it got hot, it
started to melt the adhesive and started to smell or smoke. Maybe it
was getting too hot too fast, because the wire was shorter than it had
been and partially shorted, but anyhow, I figured if I tried to take
off the tape, too much adhesive would stick anyhow.

And I don't think we could afford to buy me a roll of enameled wire.
Nor did I know any place that sold such stuff.

Anyhow, getting there is more fun than having a motor. I did my best,
even if I failed. I wasnt' upset.

-larry / dallas


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