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Author Topic: Bulb life James S. Mellen Film Handler Posts: 22 From: Sandpoint, Idaho, USA Registered: Jan 2004 posted 04-29-2005 05:17 PM                     I have been trying to improve the brightness of a Xetron XCN-35 2kw which had an incorrectly installed heat filter. The glasses were not angled which bounced the heat back to the anode and damaged 2 bulbs (and possibly the reflector). Now that the heat filter is correct and the reflector is cleaned and polished (but probably still far from right), will the bulb life be shortened? Also, does anyone know the correct spark gap for an S. Antonino HV igniter? This is an external spark gap. When one of the bulbs failed, the unit was on autostrike and kept trying to re-ignite the bulb until the spark gap contacts got pretty fried.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 04-29-2005 05:57 PM                       quote: James S. Mellen does anyone know the correct spark gap for an S. Antonino HV igniter? As long as it's firing, that's all that matters. You can screw the points in a couple millimeters if you want to get back in the ballpark with the factory setting. The particular gap distance (up to the point where it doesn't fire) will only change the resonant frequency of the tank circuit it's in, and I don't know that xenon bulbs are sensitive to that. Or sound systems. As long as the circuit oscillates (fires), you're okay.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-29-2005 06:12 PM                     In some cases corona effects can happen that deter ignition if the gap is set wrong Also the ignition is much noisier than one would like  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 04-30-2005 10:41 PM                       With a gap great enough to cause that, I would think mis-firings would be fairly obvious. A few millimeters off one way or the other should be negligible.  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 05-01-2005 07:03 AM                     The width of the spark gap determines the frequency of the current to the Tesla coil. Opening the spark gap lowers the frequency and therefore makes the filtering components less effective. Without the filtering and isolation effect of these components, the radiation of noise is greatly increased and the efficiency of the Tesla circuit may be compromised resulting in lower voltage than required for striking the arc. KEN  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 05-01-2005 08:30 AM                     James, how was the heat filter incorrectly installed? I've never heard of bulbs being damaged this way. For example, the heat glass in a Century JJ (4Kw bulbs) I ran was mounted at a right angle, straight to the path of light. I never had a problem with heat reflecting back.  |  IP: Logged James S. Mellen Film Handler Posts: 22 From: Sandpoint, Idaho, USA Registered: Jan 2004 posted 05-01-2005 09:09 AM                     The split glasses were installed so that they were flat instead of angled. As I understand it, they have a dichroic coating so that they reflect IR and pass other frequencies. If they are flat, the IR bounces back to the anode of the bulb causing it to overheat. In our case, the anode connection of the bulb melted.  |  IP: Logged Kevin Orman Film Handler Posts: 24 From: Sompting, Lancing, UK Registered: Mar 2005 posted 05-01-2005 01:05 PM                     I must say I've never heard of this before either, but I'm not an engineer.. More likely to be poor lamphouse cooling or loose anode connection. A colleague suffered repeated 'early' lamp failures until he discovered the lamps were being left 'loose' in the fitting when they were fitted!  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 05-01-2005 01:35 PM                       quote: Kenneth Wuepper Opening the spark gap lowers the frequency and therefore makes the filtering components less effective. Good call, Kenneth! While this is absolutely correct in theory, I have not noticed any differences in practical operation -- not with the small degree of discrepancy I am talking about. My experience has been, if it oscillates, it works. You set the gap close to what a new one looks like and you're in business. It doesn't have to be hand-wringingly precise, it's a fairly low-tech application. Besides, the gap isn't usually specified, anyway. So the manufacturers aren't worried about it.  |  IP: Logged Frank Dubrois Jedi Master Film Handler Posts: 896 From: Cleveland, OH Registered: Mar 2005 posted 05-01-2005 05:01 PM                    Is there a certain amount of time specific bulbs should be lasting? No matter what wattage we use 2k 3k 4k 4.5k etc, we get about 1800-2500hours (max). I heard somewhere that the 2k bulbs should be lasting close to 5000 hours?? True?  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 05-01-2005 05:43 PM                     In all the theaters that I service that use 2K bulbs, they average between 2000-3000 hours. It depends a lot on ventilation, amperage and other factors. A lot has to do with ventilation. We use 1K bulbs and easily get 5000-7000 hours on them. We keep the the lamps on all day and have great ventilation. We also start the amperage low and increase it as the bulb ages.  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 05-01-2005 05:55 PM                  quote: Tim Reed As long as it's firing, that's all that matters. That's basically true. The spark gap distance determines the amount of power/voltage of the lamp ignition and has very little to do with operating frequency...that's determined by the LC resonate circuit. As was mentioned, an igniter is basically a Tesla coil - a LC device with distributed-inductance and fixed capacitance acting more like a RF transmission line than a tank circuit. It is most efficient when the coil winding length is tuned to the resonate frequency peak and not at a node. In many BIG Tesla coils, they use a synchronous rotary spark gap operating (sparking) just in time to excite the coil and then recharge the cap of the tuned circuit. Bottom line: if it's sparking... it's working assuming no other problem elsewhere.  |  IP: Logged Glen Rich Film Handler Posts: 55 From: Nedlands, Western Australia Registered: Feb 2002 posted 05-02-2005 04:13 AM                     We are using Ushio xenons. 2.5kw in cine 2 which averages 6100hrs each lamp, and 3.6kw in cine 1 which averages 1900hrs,(I do the change of lamps when they either start to pulse or dim.) We do have a ridiculously powerful exhaust fan in cine 2 which keeps the lamphouse fairly cool to the touch. The manufacturer recommends changing out lamps at their warranted life plus 25%, which for the 2.5kw lamp would be 1500hrs, 1250hrs for the 3.6kw.  |  IP: Logged

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