"Samuel M. Goldwasser" wrote in message
...
See: http://repairfaq.cis.upenn.edu/Misc/cflhole1.jpg

This is a ~1 mm hole in the glass near one of the filaments.
Something got hot enough for the glass to melt, and after
that, as they say, the rest was history.

I've seen this on 3 CFLs in 3 different lamps/fixtures. There are no
known
problems that could account for such nasty behavior. They were all high
mileage, so perhaps the filament at that end of the lamp opened resulting
in the discharge going to one post, near the glass, or something.

The CFLs were all from GE but I don't know if they are of the same
ballast/lamp design.

Comments welcome.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above
is
ignored unless my full name AND either lasers or electronics is included
in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Sounds like a hot blob of tungsten or emission material was ejected from the
lamp's cathode. An arc could certainly do that. It's common in
incandescent filament lamps that arc upon failure; but I wouldn't have
thought that there's enough energy available in a low-wattage CFL to do it.
What were the wattages of the lamps?

But, there were some arcing problems with T5 and some T8 lamps a few years
ago when operated on instant-start ballasts. At end-of-life, the cathodes
failed and an arc started chewing away at the cathode mount wires. Things
got hot, lamps cracked and lamp holders were charred. This all resulted in
the development of ballasts that shut the lamp off if an arc was sensed so
as to avoid the mess of cleaning up broken lamps and the concern that
sputtering lamps, smoke and the smell of overheated plastic caused.

Terry McGowan