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Author Topic: Acceptable Ripple Current for 7k Lamps Bob Brown Expert Film Handler Posts: 146 From: Grand Rapids, MI Registered: Apr 2002 posted 05-09-2004 12:59 PM                        Anyone know what the acceptable range of ripple current allowed for the 7K SR projection system using the Miller rectifiers? I am starting to get arc flicker just after 100 hrs. I checked the ripple current at the rectifier and I am getting a reading of 200Mv. For the record I am using OSRAM XBO Lamps. Power settings on the rectifiers are set at 160 amps 43 volts  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-09-2004 01:51 PM                     Sounds like you are ok for ripple at that level though it would be better to measure the ripple current rather than the ripple voltage  |  IP: Logged Adam Martin I'm not even gonna point out the irony. Posts: 3686 From: Dallas, TX Registered: Nov 2000 posted 05-09-2004 02:42 PM                     With Osram 7K lamps, I've always seen flicker start at around 200 hours. I thought you guys were going to give Christie 7K lamps a try?  |  IP: Logged Bob Brown Expert Film Handler Posts: 146 From: Grand Rapids, MI Registered: Apr 2002 posted 05-09-2004 03:20 PM                        Adam, Been there done that, no difference. I think the next move for IMAX is installing some filters on the rectifiers in hopes that it will help. Grand Rapids is really bad, and mine here in Lansing are starting to have the same problems as in GR.  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 05-09-2004 04:12 PM                  You may be over-cooling the lamp...check the lamphouse exhaust airflow. >>> Phil  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-09-2004 05:37 PM                     To think that Imax is still using converted arc welding rectifiers is a gas..... there's much better available than that for that current level of operation, and it comes right off the shelf! You also need to pay as much attention to inrush current as the ripple current. As Gord says only measure it by the current method as this is the only meaningful measurement. Many rectifiers will exhibit different levels of ripple at differing operating levels. I also agree, switch to the Ushio's and give them a try.... overall, I can't think of anyone that gets very decent life span out of a 7kw lamp. Probably the best 7kw life span I've seen though is with all Christie stuff... lamp, rectifier, lamphouse. Mark  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-09-2004 05:43 PM                     typically the Millers have proven themself to be an excellent rectifier With the Ultra80's I usually get about 700hrs on the 7K lamps before they get changed  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-09-2004 08:58 PM                     I agree thry're good rectifiers, but I am just amused that Imax hasn't developed their own when you look at all the other developments thay've done. Mark  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-19-2004 06:20 AM                     Gord, Whos 7K lamps are you using? Steve  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 06-19-2004 04:33 PM                     We are using OSRAM's right now and before we had Superior Quartz The rectifiers are strong switchers with Ultra 80 lamphouses and lots of cooling  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-20-2004 12:24 AM                     I've gotten more life out of Christie CXL-70SC lamps is why I'm asking...generally Christie's are getting 2-3 times prorated warranty life presuming the power is clean. In the case of a 7K, that would be 1000-1500 hours. The 6K lamp is another trick...it is more light efficient than the 7K and tends to last longer. Steve  |  IP: Logged Dick Vaughan Phenomenal Film Handler Posts: 1032 From: Bradford, West Yorkshire, UK Registered: Jul 2000 posted 06-24-2004 03:00 AM                        We use Christie /Ushio 7kW here in our SR projectors in Bradford . Usually pull them around the 800-850 hour mark but have had them run to 1000 with no problems. Much better than Osrams  |  IP: Logged

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