50 Lumens

[JD]

granted the filiments probably just a little different which would make me think the 120's would break even easier.

Generally, the lower the filament voltage for a given wattage, the more durable the bulb. (Think car headlights and the vibration they get.) This is because the filament wire diameter is larger for lower voltage lamps of a given wattage.

which I think goes to show that there is still a significant amount of IR energy that doesn't get filtered out by reflector and mirror in the Pacific.

The IR spectrum itself is pretty wide, in other words, not all IR is the same. Heat is felt from the "low band" of the IR spectrum, whereas most IR cameras use the high band, just under the visible light spectrum. (That is why IR LEDs don't get hot.) A diachronic mirror designed to dump heat is still going to reflect almost all of the high band IR.

 

[Grog12]

Generally, the lower the filament voltage for a given wattage, the more durable the bulb. (Think car headlights and the vibration they get.) This is because the filament wire diameter is larger for lower voltage lamps of a given wattage.

Doh!

I knew that...hell I even looked at the diameter on the fillaments between HPL's 120/250. Bah this is what I get when I don't take the time to remember that the smaller the diameter number the larger the wire. Silly me.

 

[icewolf08]

Doh!
I knew that...hell I even looked at the diameter on the fillaments between HPL's 120/250. Bah this is what I get when I don't take the time to remember that the smaller the diameter number the larger the wire. Silly me.

Could be just me, and I have never worked with 240v lamps, but that seems a little back-ass-wards. Wouldn't you need a beefier filament to handle the higher voltage and not burn out as quickly?

It also struck me that I think we talked briefly about this in another thread, and i will post a link if I can find it...

 

[Grog12]

Yeah but throw the numbers into W=VA and it makes a little more sense

Using an HPL 575 for comparision

575=120A
4.8=A


575=240A
2.4=A

Remembering our trusty water analogy Amps is the volume of water flowing so more amps means we'd need a bigger pipe.

 

[Logos]

Going back to moving the Selecon lights. We're not talking about moving warm lights. We're talking about moving lights out of stock. When the selecon lights are part of the permanent rig they use less lamps than when they are rotating stock out of the store room. From the sound of it Gafftaper this won't affect you as you are intending to use them as part of your rig. I did pretty well on a couple of recent jobs and am going to reinvest the cash into half a dozen myself. Probably second hand.

 

[gafftaper]

Going back to moving the Selecon lights. We're not talking about moving warm lights. We're talking about moving lights out of stock. When the selecon lights are part of the permanent rig they use less lamps than when they are rotating stock out of the store room. From the sound of it Gafftaper this won't affect you as you are intending to use them as part of your rig. I did pretty well on a couple of recent jobs and am going to reinvest the cash into half a dozen myself. Probably second hand.

They'll be staying in the catwalks continually, moved from place to place depending on the seating configuration, and at most moved a few YARDS to hang from the rail out of the way until called on for another show.

The situation you describe makes me wonder if there is a big difference in temperature, daily temperature swing, humidity, or some other outside factor that makes life in storage harder than life up on the grid.

 

[icewolf08]

I don't understand why the Selecon's should have any lamp life issues if you move them around when they are cool. They use standard lamps (GLC/GLA), not proprietary (like the HPL for the source four). So I don't see why they would have any shorter life than the same lamp in any other fixture. The Pacific is designed to be highly efficient at cooling, and unless the lamp base itself is not stable it shouldn't effect lamp life, especially while off and cool.

 

[gafftaper]

I don't understand why the Selecon's should have any lamp life issues if you move them around when they are cool. They use standard lamps (GLC/GLA), not proprietary (like the HPL for the source four). So I don't see why they would have any shorter life than the same lamp in any other fixture. The Pacific is designed to be highly efficient at cooling, and unless the lamp base itself is not stable it shouldn't effect lamp life, especially while off and cool.

Yeah that's why I was wondering if there was something odd about the storage area the specific instruments in question were being kept in. For example if the theater has a minor temperature swing every day of just a few degrees but the store room has no AC or heat and gets wildly hot and cold.

or they are striking the instruments and hauling them off to storage 20 seconds after turning them off...

it doesn't make much sense beyond that.

 

[Logos]

Like I said earlier, this was hearsay. All I can say is that they are convinced it's true at the Festival Centre here in Adelaide. I don't understand it either. I'm still going to buy some and my main business involves moving lamps around I'm a small scale hirer.

 

[JD]

Like I said earlier, this was hearsay. All I can say is that they are convinced it's true at the Festival Centre here in Adelaide.

Generally, when quartz lamps are new, and the tungsten is freshly drawn and even, it is very durable and will not break cold when subject to vibration. (Tungsten is brittle by nature.) As the lamp ages, the re-deposits from the halogen cycle become uneven. Under a microscope, it starts looking like rock candy. These sharp crystal edges make the filament more susceptible to fracture when bent during vibration. In other words as the lamp gets older, cold vibration can become a bigger factor in what ends its life. This is one of the reasons what a re-lamping program becomes important. If the lamps are changed out at 50 to 60% of their rated life, than the reliability radically increases. This begs the question of what to do with all the old lamps and how to offset the cost. One well known lighting house (name left out) would sell the lamps on Ebay as used and from what I saw was able to recoup about 30% of the price. Not sure how I feel about that one, but I am sure it helped balance their books. I guess there are many garage bands out there that were thankful for the cheap price and were unlikely to be bothered by the lower reliability.

As to why this fixture would be more prone to the problem, I don't know.