Just found this on another list.... haven't tried it
myself (yet), but maybe it is of interest for someone.

73  Alberto  I2PHD
-----------------------------

I did break a Litz wire once and tried the aspirin-tablet-as-flux trick
and it worked like a charm.  For Litz wire to repair correctly, I think
you have to connect as many strands as possible.  To use aspirin, take
the hot iron to the tablet and melt a lot of it and transfer it quickly
to the joint to be soldered.  The aspirin dissolves the insulation so
you don't have to worry about trying to strip wire as fine as the hair
on a gnat's eyebrow.

This amazing cure supplied by someone on the r-390 list.