[Shop-talk] xmas lights, shunts, and magic

[Randall]

> The story on the box is that the shunt gets clogged up like a drain. 

Well, apparently that isn't too far from the truth.  According to this:
http://www.planetchristmas.com/Minis.htm
(scroll to the explanation at the bottom)
modern Xmas bulbs do have a kind of shunt built into the bottom of the bulb,
that is supposed to short out the bulb if it sees full line voltage (due to
the filament being burned out).  With a bad bulb shorted, the other bulbs
continue to light (somewhat more brightly, since they now get a larger share
of the line voltage).

But if more than one bulb fails while no power is applied (from rough
handling), then the bad bulbs never see full line voltage and the shunt
never gets activated.  Most likely, your "fixer" sends a high voltage (but
low power) kick through the string, to try to get the nearest open shunt to
close.

-- Randall