Exceptions to under driving bulbs question.

[Juggernaut]

Is it ever bad to under drive any Incan light, I didn't think it was but, about a week ago I took my Bigbeam 1766 C "with Par 46, 4017, 5.5 volt duel filament bulb" and tried to see how much duller it would be running off of a 6 volt, 8F Alkaline lantern battery "normally it uses a 903 7.5 volt battery" any way I hocked up the 6 volt and ran the light on high 11.5 watts and low 3.5 watts for about 3 minuets. Anyways I then preceded to put the old 7.5 volt battery back on and I hit the switch on low and just like that in 5 seconds the bulb blew! "by by $20 bulb:mecry:" So did running the bulb on less voltage damage my bulb, or the transition back to the correct voltage? What happed? Is it possible that my bulb finally decided to die exactly at that moment, I mean it's rated for 100+ hours, I did buy it used "though in perfect condition. Could it really have just been bad timing? Note: I can not see any damage to the filament, it still looks intact:thinking: and, obviously the high beam still works.

 

[mdocod]

My gut instinct on this says that it is simply a coincidental circumstance. In almost all cases, underdriveing a bulb, will result in increased life. Running it low for awhile, then switching it back to normal *may* , and I stress this is a HUGE *maybe*, may have somehow contributed to a pre-mature failure, but more than likely it would be very hard to reproduce the failure without hundreds of samples following the same procedure.

Now, it should be noted, that bulbs are often optimized for a particular life range target. A bulb designed to operate for 100 hour may have it's various fill gases optimized to complete the halogen cycle most effectively at a filament temperature that is to be expected at the design voltage. Straying from the design voltage can result in the halogen cycle not operating at it's peak efficiency. Even taking that into concern, decreasing input voltage, will, in almost all cases, increase life, but it won't always be very predictable.

Eric

 

[lctorana]

...and I hit the switch on low and just like that in 5 seconds the bulb blew! "by by $20 bulb:mecry:"...

I feel your pain. I had a run of blown 4547s a few months back myself - standard battery and

 

[Juggernaut]

I feel your pain. I had a run of blown 4547s a few months back myself - standard battery and

Ya to bad PAR bulbs are so expensive.:shakehead What I hate is the fact that you can buy a 4546 for $8 and a 4547 cost $24, I mean how drastically different are they? It must be about supply and demand or some thing.

 

[Gunner12]

Underdrive should lengthen a bulb's life.

Maybe it was coincidence. I don't see any reason why the bulb will burn out when driven at the right level(well, before when it's supposed to burn out).

 

[pertinax]

Coincidence, almost certainly. There's no obvious mechanism that would damage the filament or envelope under low-voltage conditions.

Things happen. Sorry to hear about it though.