Re: Dissecting CFLs

[andrew@xxxxxxxxxxxxxxxxxxxx (Andrew Gabriel)]

In article <oc6dnZZ8J-A-3PjbnZ2dnUVZ_q3inZ2d@xxxxxxx>,
	"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> writes:
> "Andrew Gabriel" <andrew@xxxxxxxxxxxxxxxxxxxx> wrote in message
>
> <stuff snipped>
>
>> Nothing that fancy -- just a screwdriver, knife, and pliers.
>> Some come apart along the seams, others are solvent welded.
>
> Tried that, was afraid I might break the bulb.  It turned out to be rather
> easy to freehand a cutoff wheel around the slot at the top of the plastic
> "components bay."  A few side cuts and it popped out, although I did break
> or cut one of the wires to the tube.
>
> I was surprised to see no apparent component damage.  There's a nick in the
> transformer insulation, but I think it was my doing with the Dremel.  The
> can-type capacitor had a slight bulge on top, but nothing like what I've
> seen in dead ones.  While this is not the old lamp from the Taiwanese
> formula theft era, the capacitor looked like those that I have seen on
> failed motherboards.

So do all electrolytics.

> I'll bet those bad capacitors got around more than
> anyone realizes.  It's only PC builders that regularly inspect boards
> closeup that might have even noticed it enough to raise the alarm on the
> web.  I really expected to see a fried component.  There's a strong smell of
> overheated plastic inside, but these things run hot normally.

Capacitor failure is common in CFL's because they are operated
above their temperature rating. This isn't normally a problem
because they are only required to work for something like 10,000
hours, whereas an electrolytic operating within its temperature
range would last very much longer than required in a CFL.

I've seen a couple of capacitor failures in CFL's, and in neither
case did it cause the lamp to stop working. It caused the lamp
to take longer starting and to run dimmer. It is possible that
some other control gear circuits might cease working if the
capacitor dies.

> I think this tube is still good.  It flickers when I hit it with a static
> shock.

The common failure mode for a fluorescent lamp is that the
emission material is all worn off the tube electrones (forming
the dark marks at tube ends). This will not have any impact on
a tube flickering when exposed to static. A while back, I added
detailed description of the common tube failure modes to the
Wikipedia fluorescent lamp page:
http://en.wikipedia.org/wiki/Fluorescent_lamp#Mechanisms_of_lamp_failure_at_end_of_life

> Do you have any thoughts on whether the trickle current from an X-10
> appliance module could cause premature failures in CFLs?  I've been

Yes, if the tube is flickering at all, even dimly.
That can wear it faster than when it's fully on.

> experiencing an ever-increasing failure rate.  I suppose I need to run side
> by side test of a bulb switched on and off by mechanical timer v. a X-10
> timed bulb, but I've already got way too many science project on the list!

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]