🚀 go-pugleaf

>>in these new fangled "halogen" lamps.  The tungsten chemically
New fangled they are not. The have been around quite a while.
>>contacts the hot filament, the chemical bond is broken, and 
>>the tungsten is re-deposited in the filament.  These lamps
>>won't last forever, because the tungsten isn't deposited
>>at the same spot it came off the filament.

One thing that has bothered me about these Halogen lamps with the
dimmer is, from my experiance if the bulb is not kept at least at
a certian high temperature they will fail faster. I have seen halogen
bulbs grow tungsten crystals on the ends of the filament when run at
a lower then rated voltage. Apparently this is because when the
filament is at a lower temperature the tungsten is not redeposited
on the filament while the bulb is operating. When it is turned off
and the gas cools it is deposited at the coolest point. In this case
the ends of the filament. The crystals grow depleating the material
on the rest of the filament. Hot spots do occur but there is always
some tungsten trapped in the gas when the bulb is turned off it cools
and again is deposited on the crystals. The bulbs we used where rated
at about 5000 Hrs. Most of them lasted about 2000. Some lasted as little
as 500 Hrs. These were bulbs rated at 12 Volts being run at 10V.

I wonder if the manufactures of these lamps know about this?


-- 
                                                Bob Tidrick
                                                GPID Engineering
                                                Tektronix Inc.
                                                Wilsonville OR.