"Ian Field" wrote in
:


"David Lesher" wrote in message
...
"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates
to one
end of the filament leaving weak spots at the other end where it
becomes thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?

The migration is extremely lumpy so you still get weakened spots on
the relatively thicker sections of the filament, and I vagely remember
the book I read years ago explaining why reversing the DC doesn't help
as much as you'd expect - unfortunately I can't remember what that
explanation was.




if the lamp has a transformer,why is the bulb running on DC?
transformers output AC.
you would have to add an extra component(diode) at more cost,and for lesser
performance.

Or is the "transformer" actually a AC-DC switching converter?
I have a LED gooseneck desk lamp that has an AC-DC switching converter,in
the line plug.

--
Jim Yanik
jyanik
at
localnet
dot com