Well, guys,

It appears, after a 36hr charge, operate, recharge, operate session, that
the unit is as good as new.

I never would have thought that a corroded/dirty contact would have been the
cause, what with years and years of good service from all sorts of radios
with rechargable power supplies.

The toothbrush was very, very soft, btw,

Live and learn.

Thanks for all the help.