Why'd this lamp die?


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Just wondering, I've had two 500 watt BTL lamps die on me recently. My question is, old age, and time to die, or did they get jarred while running, or while hot, or while they were being moved recently? I tried to get a good picture, but I'm not that great. Take a look at it though, and I'll describe it too.

You know how on a BTL it's like a box, with wire on two sides, and bars of glass for the other two, and a net of tungsten in between? Well the net of tungsten is in one piece, rattling around in there, and the bottom glass bar is in one piece with all the hooks to hold the net up still in there. The top bar fell apart in the middle, so a glass chunk with the hooks in it is rattling around too. Of course, it doesn't work :) The glass is perfectly clear--no smokey spots or bulges or anything.

The other lamp, which I did not get a good picture of, is nearly the same, except on the top bar of glass, only one side shattered off, and there is some smokey wisping on parts of the glass-it just makes one part of the glass appear a little frosty, but it's not much, or very dark.

120 volts here in the US, but each dimmer pack (NSI NRD-8000) has a 240 volt feed to it. Edison plugs to each fixture. Fresnels, 6 inch. 1200 watts available to each channel, but with 2 500 watt Fresnels, that's only 1000. The lamps died at different times, and I am not sure if they are on the same channel. Each one quit working after being moved, which makes me wonder, along with the facts presented above, if they were moved roughly, and that broke the lamp, rather than they lamps burned out.
Were they by any chance moved when they were hot?
They wre not moved, as in relocated, when hot. They could have been jarred, for example, if someone moved one of the legs on the side of the stage, and grabbed it so that it tilted, and one side hit a batten, but one of them died and I know it wasn't jarred, because it was on a higher truss that could not be hit by a leg. When they were moved, they were not hot, they had been sitting there for atleast 24 hours, unused.

And, when being moved, I guess that fresnel and leko lamps are more prone to dying, more fragile? I've had a par can sitting on a wooden baseon the ground kicked several feet, and it actually fel into several pieces (it was a human video (drama) and one scene was a gunshot scene, and the people on stage ran out, one of them kicked the light that he didn't see-it was covered with glowtape, and on, but oh well....) but it worked fine afterwards.

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