On 12/14/2012 10:32 PM, Phil Allison wrote:
"Phil Hobbs"
Phil Allison wrote:


** The simple fact is that halogen lamps do NOT have especially long
lives -
any more than non halogen lamps with the same filaments.

You're right about the halogen being there to keep the glass clean, but
not about the longer life. A 3400K mogul-base photoflood, like the ones I
used to use in the 1970s, has a lifetime of about 25 hours.

** Really ?

What is that supposed to prove ? ?

Is that not a 120V quartz-halogen lamp ???

A 24V, 150W, 3300K QI ( 35mm slide) projector lamp has a rated life of 50
hours.

Such lamps have been in use common since the late 1960s.

No, it's apples-to-apples, as I said. The mogul-base floods were just
like really big, ordinary incandescents. Thin glass, low pressure argon
fill. No quartz, no halogen. The envelopes got black really fast, even
though they were much larger than normal medium-base bulbs.



The high gas pressure inside quartz-halogen bulbs is what requires the
very thick quartz envelopes. High pressure slows down the diffusion of
tungsten vapour away from the hot spots, so that metal is selectively
redeposited near where it evaporated.


** ROTFL.

It is NOT in the SAME places and huge gaps open up.

See the pics on Wiki.


It isn't a perfect solution, because otherwise the bulb would never
fail. So what? The numbers are as I posted--about a 20x lifetime increase.

You're out of your depth on this one, Phil.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net