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This topic comprises 2 pages: 1 2
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Topic: Super Lumex Amps question
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Randy Stankey
Film God
Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99
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posted 07-15-2011 07:54 AM
Amps/current is a little bit of a moving target. There is a limit to how much current a lamp and a lamphouse can handle but you can't say that 90 amps or 100 amps is exactly correct for any given situation. Current will fluctuate within a certain range, even if you have a regulated (switching) power supply. With a switcher that range will be smaller, sometimes only an amp or two, but it can still fluctuate.
As Louis says, multiply amps * volts to get watts. Set the current so that your wattage is in the range you need.
Personally, I set my wattage to be around 90% of the lamp's rating but I sometimes pull that back to 85% and, if the lamp runs best at a hair bit over the rating (only by just a few watts) I'll go with that. Remember, running a lamp at 100% all the time is like driving a car with the engine at full throttle. Yes, your car can do it. It was designed to go that fast but, if you value your car, you won't run at full throttle all the time because it's not going to last as long. Same thing with a xenon lamp. Yes, it will run at full wattage but it will last longer if you take care of it and don't run it full-out all the time.
If you have a dark movie like Harry Potter and you need to brighten the picture, go ahead and throttle up if you have room but don't do it all the time unless you need to.
Other people do things differently but this way has served me well for 15 years and I rarely have trouble with xenon lamps or power supplies failing prematurely. I believe it's has a lot do do with the fact that I am conservative in the way I run things.
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Scott Norwood
Film God
Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99
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posted 07-15-2011 09:57 AM
Everyone seems to have a different theory on this.
Mine is that bulbs tend to produce less light output over time, and that this is not desirable. Therefore, I tend to start new bulbs at somewhat less than the maximum current, and then raise it gradually over the life of the bulb.
For example, with an Osram XBO-2000W/H, I would generally run a brand-new bulb at 75 amps and would gradually increase that to 85 amps (the max) as the bulb ages. In theory, this should smooth out the change in light output over time. I have no proof of this, but I also believe that this approach reduces flicker. The exception to this would be in 2-machine booths, where lamp current needs to be adjusted to match the output on both projectors.
I currently do not rotate bulbs. In the past, I have seen no benefit to doing so, and have found that they often start to flicker when rotated (why?).
And, yes, I know that the stage lighting people tend to become apoplectic when people refer to "lamps" as "bulbs." Sorry.
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