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


If you are inclined to email me
for some reason, remove NOPSAM :-)

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.

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

-larry / dallas