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Re: Replacing CF Lamps

Tom Wood said, in part:

"> BTW,
> there are no 'filaments' in fluorescent lamps, do you mean the
> electrodes at
> each end?

Well some flourescents actually have no filaments and just have a
single pin on each end of the tube that functions as an electrode. 
These are not the most common type of flourescent.  Other flourescents
do have filaments.  If there are two pins on the end of the tube (or 4
pins on a PC since both "ends" are folded around to the same side) then
there are indeed filaments.  Next time your're ready to throw a bulb
out, crack it open, go away and wait for the glass dust an mercury to
settle, then come back and look at the interior ends.  Voila --

These are energized before the high voltage is applied that sends an
arc across the tube -- this is done in a mumber of ways -- from lamps
with the little thumb-sized starter, to rapid start lamps, to bulbs on
electronic ballasts.  The heat helps to vaporize the mercury to make it
more easily ionized.  In some cases the filaments have current running
through them from one end (of the filament) to the other all the time
--rapid starts (or pre-heats) are like this.  In some configurations,
when the bulb is lit, the current shorts across the tube to the other
electrode instead of traveling all the way through the filament. 
Conventional starter lamps work this way:  When you turn on the lamp,
current passes through a choke coil, then through one filament, through
the starter, then through the other filament, then back to the AC power
source.  Since the starter has a bimetalic strip inside, after a few
seconds, it warms and opens the circuit, collapsing the current in the
coil, which cause a high voltage arc across the lamp, and the filaments
act merely as electrodes and the starter remains out of circuit until
you turn the lights off then on again.  In all of the bulbs, they ends
act as electrodes when the bulb is lit.

Scott H.

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