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Author Topic: Xenon off or on? Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 04-24-2003 05:44 PM                     Going with the rule of thumb that each strike kills off an hour of lamp life, what happens if I turn the lamp on for a 2hr movie and then shut the lamp off? Have I killed off two or three hours?  |  IP: Logged Erik Stevens Film Handler Posts: 10 From: Melbourne, Victoria, Australia Registered: Nov 2002 posted 04-25-2003 06:53 AM                     If spoke to our Osram representative a couple of years ago, and was stressing the point that all elements of the bulb must be cold before restriking, otherwise you are doing the bulb damage. On average, a lamp will take half an hour to an hour to 'fully' cool down. As we have good airflow through our lamphouses, I use a happy medium of 45 minutes. If the turn around time is less, I will leave the bulb struck, if longer, I will switch it off. We have two types of projectors on our circuit - Kinoton & Cinemecannica. As they use exactly the same bulb, you can see the extended lamp life in the cinemecannica lamhouse, as the bulb can be left on continously. Unfortunately you can not continuously leave the bulb on with the Kinoton (without making modifications). Thus striking between sessions, and thus seeing shorter lamp life. Ciao, Erik  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 04-25-2003 06:40 PM                     This is interesting because after about 10-15 mins my 2kW lamps are cool to the touch. Maybe my cooling system is just that intense.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 04-25-2003 10:54 PM                     Manny, are you being serious? I assume you're not actually touching the lamp's quartz envelope with your bare hands. One would expect the anode and the cathode to stay warm longer than the quartz envelope. Generally you should allow about 30 minutes of cool-down time for a lamphouse before openning it. Also, remember that it's quite possible to over-cool a xenon bulb; they require less cooling than carbon arcs do. Osram says (page 25), "Excessive cooling is not good because it too can bring about increased arc instability due to turbulence in the lamp bulb. If the lamp voltage with cooling falls by more than 1 volt compared with uncooled operation, this normally means that cooling excessive." (I'm not sure how they expect you to measure uncooled operation, though, since it implies defeating the safety interlocks of your lamphouse.) --jhawk  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 04-25-2003 11:03 PM                     Well actually, I only change lamps in the morning before opening. My senior tech is the one who goes around testing Xenon lamps. And, no, he's not using his bare hands. He uses his tongue. As for cooling, I have to assume that everything is kosher because we get a lot of mileage out of our bulbs.  |  IP: Logged Bob Healey Film Handler Posts: 93 From: Milford, CT Registered: Sep 2001 posted 04-25-2003 11:31 PM                     Running 6K changeovers here, the lamps are struck at 6:30 PM, left on for three shows, then turned off after the last reel on the projector has run. The booth gets nice and toasty, but running 3 nights a week gets 2-3 years/lamp. In addition, the lamp houses can be tempermental striking depending on what other equipment is powered up (lamp one only strikes nicely when 2 is lit, 2 only strikes nicely when 1 is off)  |  IP: Logged

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