Please consider, a 1000 watt 240 volt T19 on a dimmer{for 120v thinkers just halve all the figures} It has a cold resistance of 3.8 ohms and a hot resistance of 57.6 ohms. A typical dimmer will feed 1.65v at "0" and drive .35A putting 2.24 W into the lamp of preheat.
@ 13V you can see the barest glow in the filament and are drawing .96A and 12.6W
@30V you can see a real glow and are drawing 1.5A and 45W
at 60V you begin to get some output but at 1/4 voltage you are drawing 2A or nearly half the "full" current
@80V which is 1/3 voltage you are drawing 2.3A which is more than half the full load current and is also the point at which the dimmer starts to interact with the other dimmers on other phases.
This is why running all your dimmers at 1/3 is the worst thing you can do to your neutrals.
Now there is a benefit in Pre-heating 2k and 5k in the previous cue, in effect you are moving them up the dimmer curve, but I have experimented with lamps and the increased resistance only lasts for a few seconds with 1/2k and a couple of minutes with 2k"s.
The thermal mass of a theatre lamp has to be as low as possible to enable it to light up and dim quickly, and pre-heating is not logical, especially when all your dimmers are "leaking" a few watts of heat anyway, so by all means turn on your lights to check them but be aware you are not helping to increase their lives and are probably shortening them and wasting a hell of a lot of power in the process.
Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?If there's one thing I've learned from this thread:
Check lamps often.
Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?
Sorry but your assumption that the lamp blew because you did not preheat has absolutely no validity, it blew because it was at the end of its life, we all try to explain things that fail but mostly it is just serendipity, of course we all do lamp checks before a show, that is normal practice but it should not be confused with preheating which I have shown to have no basis or benefit in fact.
Industry standard is once a day before the first performance, even in Las Vegas; but I'm not sure about Broadway. SteveB?
Here's another argument for NOT pre-heating: if a lamp is near the end of it's life due to a weakened thin portion of its filament, isn't it better to "bump to full" during the lamp check, so it can be replaced before the show and not fail during?
Myself, on long running shows I write a cue that takes everything up to from 0 to 10% in five minutes, which gives me time to get to the stage and roughly check for burn-outs, then runs an effect which brings each channel to full for roughly 10 seconds to check for focus (some channels longer, some shorter), then puts me in Q1 for House Preset. I've still had lamps blow this way, so it may be the best of both methods.
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