Michael Daly wrote:

On 3-Feb-2004, "Oldylocks" no wrote:



I just don't know if I've ever
seen a black burned-looking spot on a bulb like that. Maybe it's just about
to burn out?



It's not that uncommon, though you're probably more familiar with frosted
bulbs and don't notice. The filament will keep losing material and it coats
the glass. Once it gets too fine, one surge (as in turning it on) will cause
it to pop. Some types of bulb get coated thicker and faster than others -
Mini-Maglites (IIRC - krypton bulb) look silvered by the time they reach the
end of their life.

Mike


I'd expect that as the filament lost material it's resistance would
increase and the wattage dissipated would decrease, so it wouldn't get
"hotter" towards the end of it's life.

But, maybe the coating on the inside of the glass doesn't let the heat
pass through as well as clear glass, so the bulb glass gets hotter when
it's coated?

The OP didn't say what parts the manfacturer is replacing. Maybe there's
just something wrong with the plastic so as it ages it either smells
when warm or changes so thatm it absorbs more light and heats up to the
point where it smells. Or perhaps some foodstuff go smeared onto the
plastic and then got rancid?

Too many variables here, 'eh?

Just my .02,

Jeff

--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"My luck is so bad that if I bought a cemetery, people would stop dying."