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Author Topic: Xenex lamp problem Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-06-2009 09:53 AM                     I had also measured the voltage from the breakers. 120 volts. Coming out of the contactor was also 120 with it engaged but lamp not lit. I read 211 volts across the phases. Also remember as in my original post, this was never an issue before. They never had ANY problems lighting the bulb. This had all started pretty much the day after everything overheated over the summer when the exhaust failed. Since then, it has been 2 or 3 new bulbs that they have tried. The other thing yeaterday that I noticed is that a couple times while striking it looked like it lit for a split second and went out. Maybe that's nothing but I thought I would throw that in.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 10-06-2009 11:11 AM                        I saw this same issue at a theatre with Cinemecannicca (sp?) consoles and IREM rectifiers. After changing out everything else we finally changed out the transformers and the problem went away. I really don't know why it fixed it but it did.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-06-2009 12:27 PM                     possibly the filter cap failed or got flaky  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-06-2009 02:43 PM                        |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-06-2009 03:43 PM                     Tim. I'm assuming that's the relay toward the top of the rectifier mounted directly onto a board with 4 wires on it? If so, what is the purpose of that relay?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 10-06-2009 07:49 PM                        I'm with Time. TEMPORARILY connect the red-to-red, black-to-black. If ignition is good, then repair/replace that relay. Happened 4 times in 37 years. 85 volts is enough if all is well. I have never added a booster, ever. Osrams (& probably Christies) work OK. Life is 6k+ hours. Louis  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-08-2009 01:06 AM                       quote: Richard May what is the purpose of that relay? It adds additional capacitance to the output for ignition. The symptoms you describe are a classic failure mode of that relay. Louis described how to check it.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-08-2009 05:37 AM                     I believe it is just the opposite, Tim...it removes capacitance just for ignition to cut down on in-rush. That is...when the rectifier first turns on, all capacitance is on line, once a threshold is reached the RA (or now the A1) relay pulls in, drops out main Capacitors leaving just the boost so the voltage rises quickly...when the igniter fires, in-rush is reduced since only a relatively small amount of capacitance in the circuit to discharge across the lamp at high voltage. Presuming the lamp ignites, the voltage will drop quickly when it reaches the relays threshold voltage, the relay drops out putting the main capacitors back on line (which charged up to the threshold when you first turn the lamp on), which thus holds the arc, well filtered, the remainder of the lamp's on-cycle. As you can see, if the RA (A1) relay does not do its job, you can loose either your main filters or your boost and hence it can prevent ignition or even once ignited loose the arc if the main capacitors are not brought back on line. Jumping it out will normally restore operation but now you are going to be harder on the lamp as your in-rush is going to be much greater. Steve  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-08-2009 09:52 AM                       Thanks, Steve.  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 10-08-2009 10:17 AM                     As several people have pointed out, the Xenex lamphouses are prone to internal arcing to the metal frame at the negative end where the bulb passes through the reflector and then through a round opening in reflector support structure. I've solved the problem by using a strip of teflon about 1.75in wide x 1/16in thick & curling it inside the hole. It's own 'springy-ness' holds it in place and the teflon is able to easily withstand the high heat inside the lamphouse. You can get teflon sheets at many larger hardware or plumbing supply stores. (The white ring is the curled teflon strip) As for ventilation, IMO the stock exhaust fans on the Xenex 1 & II's are pretty wimpy. This Xenex 1 has been modified with xtra blowers for operation at 3K. (or, more accurately: a 3K bulb running a 2.8k) Additional internal 'plumbing' directs the air flow to cool the cathode & anode ends of the bulb. This modification was made over two years ago and enabled a great improvement in light output without sacraficing bulb life. (They were formerly running a 2k bulb at 2800watts !)  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-08-2009 08:46 PM                     Jim, Good idea! That mirror in there is actually pretty dam good... I once had one putitng out more light with a 3kw lamp installed then the Strong Futura running at 135 amps sitting on the projector nest to it could muster out. Regarding the RA relay... I replaced a couple of them in the locations I had problems and that was not the cure... Mark  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-09-2009 09:36 AM                     Well that relay is one of the few things that I have not checked yet. As Steve said, you could lose the arc at times when this happens. That is exactly what happens. Like I said, there have been days when they say it lights right up on the first strike for a couple shows. Then it will not light so I'll try the relay next.  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 10-09-2009 09:42 AM                     Thanx Mark. While cleaning up a storeroom behind the booth several months ago, I found these teflon insulator tubes, which I beleive were shipped with the Xenex lamhouses and were indended to be installed in that 'hole' behind the mirror to keep the negative end of the bulb from arcing on startup. I'm not sure why they were never put in place when the lamphouses were installed. Mabye next time I need to change a bulb I'll put one in; but my teflon strips are working well, and I'm a big beleiver in the old addage that says: "if it works,. . don't fix it"  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-09-2009 04:21 PM                     Mine had a black o-ring on it that fit in the groove on the outside of that white sleeve. I hope I was supposed to leave it on.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-09-2009 08:33 PM                     I believe the O ring is the newest idea of holding it in place. Used to be a 360 degree spring.  |  IP: Logged

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