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Author Topic: Overcooling a Xenon bulb in a Barco? Jay Glaus Expert Film Handler Posts: 123 From: Pittsburgh, PA USA Registered: Dec 2010 posted 03-22-2014 02:14 AM                        Just curious what everyone's thoughts here are... In our biggest screen we run a 6500 watt Ushio in our 32b, normally run at around 5800 watts or so. We have never reached warranty hours as of yet on any of the bulbs run in that machine. They either become hard to strike, dim, or uneven/unsteady arc (sometimes all of the above), right around half life. The last 6500 we pulled out couldn't even get close to the normal footlambert reading we try to keep despite turning it up to full steam. This seems to happen right at about half life on each bulb, which is only about 250 hours. When you pull the bulb out, aside from the envelope being nicely darkened in places, half of the anode is always pitted or wore way out. It's like a half moon on the anode, half of it is wore way away, but the other half in still in good shape. I know in 35, you would adjust the magnets to get the arc up so it would burn more evenly on the anode, but I do not know of any such adjustments in the lamphouse of a 32b. Correct me if I'm wrong. The only other thing I could possibly think is overcooling. I know a ways back it was believed that you couldn't get enough air movement, but later that was changed. If you can overcool a bulb in a film lamphouse, I would believe the same concept would hold true for digital, would it not? We have a 800 CFM exhaust on our 32b, which I believe to be excessive, and barco's specs state it needs 450 CFM. However, a lot of the people that sell these machines like to recommend these big powerful exhausts for whatever reason, and sometimes I can't help but think maybe a 500-600 CFM fan would be the better choice, if I am indeed overcooling the bulb. On our last screen we converted, which was a 4200 watt running in a 23b, we put on a 600 CFM exhaust. Everything seems fine, it's moving plenty of air and nothing is overheating. I'm interested to see if I get any better bulb life with the lesser fan. I realize the 4200 watt lasts longer than the 6500, but I would think if it makes it to the end of it's warranty hours without a problem, that may be a sign, as I have never made it much past half life on any of the 6500's. Any thoughts on this? Could it be overcooling? Something else? Any advice would be appreciated! Thanks, Jay  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 03-22-2014 06:28 AM                     Hi, Some Barco lamphouse have the magnet, you should check on yours. 800CFM sound good to me, what lamps are you using? Are you claiming warranty every time, and are they accepting it?  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 03-22-2014 10:24 AM                       I would doubt you are overcooling. The blackening speaks more to heat. The rating of the fan is one thing, the actual CFM is another. There could be blockages in the duct either before or after the fan. Is the room air conditioned so the temp goes very low?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-22-2014 10:32 AM                     You definitely are not over-cooling the lamp...800 cfm on a 6500 is about the minimum you should have on that size lamp. We don't have many customers running the 6500 so I can't comment on its life cycle other than those that are running the 6500 are getting their hours. One of our customers switched to the DXL-60BA2/L to get ge more rated hours (800 vs 600)...the cost savings was substantial and the light loss was actually minimal. I have hear, through the grape vine, of a bad batch of DXL-60BA2/Ls but I have not personally experienced it...they all seem to have made their hours. It might be worth a shot in your case since you are not running your 6500 full-tilt.  |  IP: Logged Jay Glaus Expert Film Handler Posts: 123 From: Pittsburgh, PA USA Registered: Dec 2010 posted 03-22-2014 12:33 PM                        Hello, thanks for everyone replying. Yes, I've been claiming warranties and for the most part I've gotten a new bulb, once I think I only got a credit off a new one, but I can't complain. We keep the booth right around 70 degrees. And I believe the duct work is good, we put it in new when we converted that screen, went from 6 inch to 8 inch. I took the lamphouse out and felt the exhaust from inside the machine and she seems strong. I'm going to see what I can find out about a possible magnetic adjustment, I think that will solve my problem if the adjustment can be made. Jay  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 03-22-2014 01:28 PM                     quote: Jay Glaus We have a 800 CFM exhaust on our 32b, which I believe to be excessive, and barco's specs state it needs 450 CFM. The minimum specs for the smallest bulb that projector will handle. Recommended > minimum Larger bulb = more exhaust  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 03-23-2014 02:19 AM                     Jay, is that 800 cfm the extractors specification, or is it measured?  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 03-23-2014 07:54 AM                     Good point Pete. Depending on the pressure your 800cfm figure may drop significantly. You'll have to check from the inside, with the lamphouse removed.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-23-2014 10:00 AM                     My specifications are always at the end of the duct before it connects to the projector. It makes it easier to measure before the projectors arrive. There will be a reduction in air flow once it is connected and that is allowed for.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-23-2014 09:18 PM                     Interesting, for this is what I'm also experiencing with one of my 4K32B with the 65BA2 bulb installed-and this one runs 3D along with HFR on a 65ft wide screen. Bulb gets close to a hundred hours before warranty and hard strikes begin to show up. The last pull I did in this house, the bulb did have a dark spot inside the envelope behind the anode. On the same breath: I busted this bulb to toss and looked at the anode, and interesting that the one small crescent corner of the anode looks like it was never used while the rest of the face surface shows the "ripple horns" and decay from strikes. It looks like the flame never completely engulfed the anode. Since that anode is almost a pound in weight by itself, could it be sagging during operation and could this cause my hard strikes when reaching age? My other house of this size is a standard 4K 32B unit that only runs 2D and I can easily meet warranty hours without any problems with the 65BA2 bulb. -Monte  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 03-24-2014 08:31 AM                     Monte...is your projector on the 1.11 or later software? That is the version that is supposed to help with lamp strikes. It not only makes the SPG more aggressive it also ramps the LPSes too. We have limited experience with that lamp due to its cost/hour...the customers we do have with that lamp have not reported any issues though.  |  IP: Logged Joe Elliott Master Film Handler Posts: 497 From: Port Orange, Fl USA Registered: Oct 2006 posted 03-24-2014 11:50 AM                     As Steve eluded to above, and no one as mentioned, your best bet is to go to Ushio bulbs. I am betting you are using Osram bulbs right now, as difficulty striking and premature blackening, and also white patterns on the glass (is that quartification?), are common with Osrams nowadays. Osram used to, about a decade ago, be the best bulbs, but they have slipped tremendously in their design.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-24-2014 01:29 PM                     I'm using the USHIO DXL-65BA2 for these two 4K32B units. I'm also going to do a test on these things if I'm getting the CFM's going up the stack, for I bet I need to add boosters on the exhaust to pull the immense heat these big lamps emits during operation. I'll check software version and report this to the install tech that we have contracted out. thx-Monte  |  IP: Logged Jay Glaus Expert Film Handler Posts: 123 From: Pittsburgh, PA USA Registered: Dec 2010 posted 03-24-2014 02:59 PM                        Well, I've checked with Barco about magnetic adjustments. There used to be magnetic adjustments in the early days of Barcos, there was a view port to see the arc's position. However, they had problems with the integrity of the view ports, and the heat from the bulb caused parts of it to melt, leaving a hole in the side of the lamp house. They sold replacement ports that were just pieces of metal to eliminate that problem. On the newer Barcos, they "redesigned" the lamp house to not need adjustments for the magnetic field, so there is no longer anything to adjust. It should be all set and work flawlessly when it arrives at your theater... it should. Barco had me pull the log files and diag package, and they are going to see if they see anything wrong in there. I'm curious though if it is just the lamp house in my 32b that's causing the problem. I have two 23b's that run 4k bulbs. If I knew you could swap lamp houses between 23's and 32's I would, but I don't know if there is anything special inside of the 32's lamp house for running higher wattage bulbs that wouldn't be in the 23's lamp house. I'd just want to be sure, that if I put my 23b's lamp house in my 32 with a 6500 watt bulb, nothing's gonna cook. I think that would be a good test to see if it's just something not right in the lamp house. As for the exhaust, the 800 CFM spec is from the manufacturer, I would like to take a reading at the machine, but I don't have a meter (aside from my hand ). I can't imagine its too far off as the fan is only about 8 foot away from the machine, and sends air another 3 foot out the far port window and thats it. I use 8 inch duct work, and the booth has cool air returns for the furnace, so it can't be getting too much resistance. I'll be interested to see if barco finds anything, has any suggestions, and if I can swap lamp houses. Hopefully, one day, I'll finally be able to run my bulb to it's warrantied hours! Jay  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 03-24-2014 05:20 PM                     quote: Monte L Fullmer On the same breath: I busted this bulb to toss and looked at the anode, and interesting that the one small crescent corner of the anode looks like it was never used while the rest of the face surface shows the "ripple horns" and decay from strikes. It looks like the flame never completely engulfed the anode. Since that anode is almost a pound in weight by itself, could it be sagging during operation and could this cause my hard strikes when reaching age? Maybe it's just a stupid hypothesis, but couldn't this be the result of an imbalance in the airflow around the bulb? Like one side of the bulb getting properly cooled while the other is running too hot? Wouldn't that also cause some minor deformations that could cause anode/cathode alignment problems?  |  IP: Logged

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