[Elecraft] smoke test

[Jim Wiley]

Ralph -


Many - not all - fluorescent  lamps (I am assuming you are  talking a 
CFL , or Compact Fluorescent Lamp) have a small  resistor used as a fuse 
for the ballast.  The ballast is in the base which supports the 
discharge tube (the fluorescent portion).  The ballast develops the 
voltages needed to initially fire the tube (when cold)  and limit the 
current once the arc is initiated.  It consists of several capacitors 
and resistors as well as a few semiconductors.  As the tube ages, the 
current draw increases.  At some point, it becomes too much, and the 
ballast fails.   To prevent a really catastrophic failure, a small 
resistor (typically a 1/8 or 1/4 watt unit) is used as a fuse.  Overload 
destroys the resistor, cutting off the current.   Why a resistor?   They 
are much less expensive than fuses, particularly at low current 
ratings!  The light from a CFL comes from a mercury-vapor arc inside the 
tube, which emits large amounts of ultraviolet light.  The phosphor on 
the inside of the tube converts the ultraviolet energy into visible light.


- Jim, KL7CC



Ralph Tyrrell wrote:
> As I sit at my computer the radio desk is to my back. I heard a burst of static behind me. That was odd since no radios were on.  The only thing on at the radio desk was the desk lamp and a power supply that keeps the batteries charged. Both are plugged into a strip that switches power to them.
>
> I went over to the radio desk and looked at my equipment, both off. Still puzzled I turned on the 2m rig, all normal. Then I turned on the K3. All normal. I turned them off again. The K1 sits by, not connected to anything at this time.
>
> Still puzzled  I sat there wondering if something had happened to my battery bank or one of the batteries.  I have three 26AH batteries in parallel. Each battery is fused before to goes to a fused buss.
>
> Then my nose began to notice the smell we all dread. Something electrical was over heated.  Still I did not noticed a symptom I should have noticed earlier, the desk lamp was off. I touched the top of the lamp and it was very hot.  The bulb, a 13 Watt Florissant had failed. The ceramic base was too hot to touch. 
>
> How often do Florissant bulbs fail this way?
>
> I had the feeling that if I were not there a fire may have started.
>
> 73, Ty, W1TF, K3 #696, K1 #1423
>
>
>
>       
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