> I've normally scratched up the surface and soldered them.
> Why is there no metal coating on the middle of the disc?
> Sounds pretty unusual to me. :o)
> -Roman

No metal. I've noticed the same thing on the piezos on ultra-
sonic tanks. The wires to those are held down with what looks
like epoxy. Under the epoxy is some kind of metal joint to the
ceramic that melts with an iron, but once melted is difficult
to remake. I'm working with small audio beepers on this little
job, not U-S piezos, desoldering a U-S was a mistake I made
once. (un)fortunately that unit was so old and decrepit and had
a fatal fault with a coil that was enough to write it off anyway so
I didn't have to re-attach the U-S wire

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