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Author Topic: Xenex lamp problem John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 09-28-2009 06:05 AM                     I would guess this is too little capacitance.... See the discussion of requirements on p.6 (p.7 of the PDF) of Osram's Guidelines For Control Gear And Igniters--ENGR_BLTN12. A booster puts its own output capacitor between the rectifier and the lamp, so it would "help," but you can probably just replace the existing capacitor(s) with a lot less effort. --jhawk  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-28-2009 06:14 AM                     When xenon lamps were first brought out in the 50's they were designed for a no load voltage around 65 volts as the years went by and the bulb manufactures changed manufactureing methods the no load voltage has constantly needed to be increased the one exception is Ushio that still spec 85v as their no load voltage  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-28-2009 09:21 AM                     quote: John Hawkinson A pair of P1-X80s Man, those are vintage Irems!! Never worked with those. Are yours single or three phase? I've mainly worked with the N3-*** series in my entire 32 years in this biz. It's interesting to note that all new IREM N-*** rectifiers have at least 110 volts no-load except the 50 amp model which is about 90 volts. Had this problem been confined to just one Irem/Xetron lamphouse/rectifier I'd have suspected something amuck there but that was not the case. I ended up installing 4 boosters in one complex. The other 4 in this 8 plex lit up just fine and had well over 100 volts DC no-load. Gord, Christie is in fact one of the lamps we had problems with pre- booster. So I can say that even a Christie lamp will not ignite consistantly on 85 volts... The other brand that didn't like the 85 volts was Osram. All lamps were either 2kw or 3kw in size. Some smallish size lamps however do fine with 85 volts. Mark  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 09-28-2009 10:35 AM                     Single. I imagine that's the P1, but who knows. --jhawk  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-28-2009 10:47 PM                     Not quite..... The Booster is a seperate DC power supply of it's own, with an appropriate sized filter to keep inrush current in check... DC is about 110 volts or there abouts. There is also a 150 amp diode on a heat sink that isolates the booster supply from the rectifier itself. Similar to the start circuit in the old Strong 68000 series but able to accomodate lamps up to about 4kw. Mark  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 09-29-2009 01:38 AM                     Umm, Mark, are you responding to me? Monte asked if a booster would help his existing machine that has 140V no-load. I think my point stands. Yes, a booster has its own supply, and yes it also has its own output capacitor (and series resistance), and that's what limits inrush current during striking. But that's not the point. In his existing case, obviously a 120VDC supply isn't going to be helpful. The only difference is in the output capacitance [and maybe the series resistance] presented to the lamp. No? --jhawk  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-29-2009 06:46 AM                     Yes, was responding to you jHawk. Monte's case is all together different because it involves a switcher, they have some capacitance but not all that much. All switcher control is electronic. I have heard of a couple of instances where line resistance was a problem and capacitance helped but it isn't going to help when you only have 85 volts to begin with as in the IREMs. In my case all the rectifiers were right next to the lamphouses or within just several feet.  |  IP: Logged Don Sneed Master Film Handler Posts: 451 From: Texas City, TX, USA Registered: Aug 2001 posted 09-29-2009 02:09 PM                        Hey I just had that problem at two different theatres....Mark is correct, check the metal piece at the reflector opening, it sounds like the arc is be sent to ground....you can check this by looking at the rear of the reflector, door open, safety switch being push in...strike the lamp, if it strikes, release the safety button & close the door...if it does not, you should see the electricity going from the bulb to the reflector, if so reposition it & all goes away...I just had this on two of the same type of lamps...  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 09-29-2009 03:59 PM                     I'm going back to the theater in a few days. It does have the metal insert in the reflector. I do have a plastic one that I will put in it's place. I'm not so sure it is that though because I do see the spark jumping the gap when trying to light. Unless the full spark is not going through the bulb...if that's possible. I may not have mentioned in my post that this DOES happen even with a brand new bulb. It had never done this before the overheating problem over the summer.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-29-2009 05:23 PM                     Richard, It would also be interesting to know what your no-load dc is at. This will also tell you the age of the rectifier too. Another hint... those older Irem rectifiers worked pretty well on ac that has a high leg. That high leg seems to raise the no-load just enough for things to work 98% of the time... theaters with 208 is where the problem lies!! Mark  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 09-29-2009 05:28 PM                     I'll check the no-load voltage. This rectifier has been in this screen since at least 1989. The other screens there have 208V.  |  IP: Logged Jonathan Bodge Film Handler Posts: 83 From: East Dorset, VT Registered: Nov 2006 posted 10-03-2009 07:18 PM                     I had a wacky thing happen once years ago relating to bulb striking. Xenex 2 Lamphouse w/Kneisley rectifier all brand new. Bulb would ignite sometimes, sometimes not. Contactor would energize, cap would fill up and reach the Zener threshold, fire and Na Da. So after many many hours and many many replacements I simply wired the automation "start" button directly to the ignitor strike. Fired every time.In other words,I would force the ignitor to strike BEFORE it was allowed to reach proper voltage. Had something to do with inrush current. Maybe someone could enlighten me on this phenomenon.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-05-2009 09:02 PM                     Okay. This is what I found today. No load voltage is 76 volts. I changed the fitting in the reflector to the plastic version which I had. Still no good. I swapped ignitors from another theater. Still no good. Checked all diodes. They checked out fine. No loose connections anywhere. The weird thing is is that the bulb sometimes will stike right up on the first shot and other times it may take 10-20 strikes or more. The other day it took them 10 minutes to get it lit.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-05-2009 09:06 PM                     The no-load is too low for reliability. Sometimes a cold lamp will light and once it's hot won't light. Is this a single screener where you could measure other lamphouses no-load? Also, did you check all the three phase comming to the rectifier starting at the circuit breaker... also inspect the breaker itself. I've seen quite a few breakers fail and cause similar problems... AC voltage might measure fine without the lamp on but once you get the lamp to light you may see one phase is down quite a bit. Another possibility is that you may have two funky lamps at the same time... but to me 76 volts ain't enough... Mark  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 10-05-2009 10:57 PM                       <squeeeal.. feedback> Hello? Is this thing on? RA relay!  |  IP: Logged

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