posted 03-21-2009 07:21 PM                    

In case anyone's interested, Osram Sylvania seems to have revised their applications guide, ENGR_BLTN11.pdf. From the Nov 1997 version ("XBO theatre lamps; Technology and applications"):


to the May 2008 version ("XBO theater lamps; Technology and application."):


Not a whole lot of differences, it seems, other than theatre/theater. One change is the "Operating duty cycle" section, which now reads:

quote:

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XBO lamps are optimized for their respective applications. Differences in design lead do differences concerning the operating duty cycle. Lamps for conventional film projection are optimized for an average operating duty cycle of 90 minutes, thus achieving their maximum life. For video projection, effect lighting applications or solar simulation, the lamps are optimized for longer cycle times. If the lamp is not in use for a short break, it is generally recommendable to keep the lamp burning if the break is not longer than 10 minutes. Lamps with extremely short arcs, which are common in video projection, may suffer from overloading of the anode if permanently operated. In this case, the lamp life can be extended considerably if the lamp is allowed a cooling phase after some hours. Ignitions do also not extend the life of XBO lamps but they damage them clearly less than lamps filled with mercury. During the ignition phase, mercury lamps operate in the lowpressure range, while XBO lamps can start cold at a gas pressure of 5-15 bar. The high pressure allows an easier startup of the XBO cathode.

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quote:

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XBO lamps have their highest life expectancy if once switched on they are not switched off again. Every additional startup, especially from cold, shortens lamp life. This is because in cold ignition -- and in this context this means everything more than 5 to 10 seconds after switching off the lamp -- the high startup current needed to set up an ignition path must be handled by the cathode in its cold state when its emission cap ability is very limited. This torture erodes the cathode tip (tungsten particles can be split off) thus altering its robust surface, and sudden local overheating can cause depletion of the doping material added to the tungsten in the cathode to improve its emission capability. At an impoverished cathode the arc wanders restlessly to and fro searching for the place where emission conditions are best,without ever finding it. The average life specifications for high-wattage XBO lamps refer to a burning time of 90 minutes per switching operation, in accordance with typical operating times in modern theatres.

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quote:

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The first criterion of adequate cooling is basetemperature. This must not exceed 230 C. The temperature is measured at the end of the base remote from the lamp. Stick-on temperature sensors or thermally sensitive paint can be used for measurement.

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quote:

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The first criterion of adequate cooling is base temperature. This must not exceed 230 C. Stick-on temperature sensors or thermally sensitive paint can be used for measurement.

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posted 03-22-2009 02:30 PM                    

quote: Osram

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If the lamp is not in use for a short break, it is generally recommendable to keep the lamp burning if the break is not longer than 10 minutes.

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Sounds like something a politician would say..full of doublespeak.

A better way of saying it would be:

"Turn the lamp off if the break is longer than 10 Minutes."

But I still disagree with that. The thermal cycling and stresses of ignition are more harmful for the bulb than leaving it burning.

I would only turn off the bulb if the break was going to be more than 30-40 minutes.

With oldschool Osrams and Christies, I have NEVER had a bulb fail when it was left on by my standards. I HAVE had bulbs fail when they are constantly cycled on and off by Osram's new guidelines.

Schmucks can't build a bulb that lasts and now they proport to be experts on getting max life out of them.