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» Film-Tech Forum   » Operations   » Large Format Forum   » Acceptable Ripple Current for 7k Lamps

   
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      Profile for Bob Brown   Author's Homepage   Email Bob Brown   Send New Private Message       Edit/Delete Post 
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

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Gordon McLeod
Film God

Posts: 9431
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 05-09-2004 01:51 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
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

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3643
From: Dallas, TX
Registered: Nov 2000


 - posted 05-09-2004 02:42 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
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?

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Bob Brown
Expert Film Handler

Posts: 146
From: Grand Rapids, MI
Registered: Apr 2002


 - posted 05-09-2004 03:20 PM      Profile for Bob Brown   Author's Homepage   Email Bob Brown   Send New Private Message       Edit/Delete Post 
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.

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Phil Hill
I love my cootie bug

Posts: 7595
From: Hollywood, CA USA
Registered: Mar 2000


 - posted 05-09-2004 04:12 PM      Profile for Phil Hill   Email Phil Hill       Edit/Delete Post 
You may be over-cooling the lamp...check the lamphouse exhaust airflow.

>>> Phil

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16062
From: Bountiful, Utah
Registered: Jun 99


 - posted 05-09-2004 05:37 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
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

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Gordon McLeod
Film God

Posts: 9431
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 05-09-2004 05:43 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
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

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16062
From: Bountiful, Utah
Registered: Jun 99


 - posted 05-09-2004 08:58 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
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

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11993
From: Annapolis, MD
Registered: Dec 1999


 - posted 06-19-2004 06:20 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Gord,

Whos 7K lamps are you using?

Steve

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Gordon McLeod
Film God

Posts: 9431
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 06-19-2004 04:33 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
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

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11993
From: Annapolis, MD
Registered: Dec 1999


 - posted 06-20-2004 12:24 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
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

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Dick Vaughan
Phenomenal Film Handler

Posts: 1032
From: Bradford, West Yorkshire, UK
Registered: Jul 2000


 - posted 06-24-2004 03:00 AM      Profile for Dick Vaughan   Author's Homepage   Email Dick Vaughan   Send New Private Message       Edit/Delete Post 
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

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