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Author Topic: Leaving a digital projector on with the douser/shutter closed
Alexis Mayer
Film Handler

Posts: 4
From: Philadelphia PA
Registered: Aug 2006


 - posted 04-19-2012 04:32 PM      Profile for Alexis Mayer   Author's Homepage   Email Alexis Mayer   Send New Private Message       Edit/Delete Post 
Is leaving a digital projector on with the douser/shutter closed bad for the projector? If so, how exactly? Is there a limited amount of time where it would be okay?

Thank you in advance for your insights!

Best,
Alexis Mayer

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Justin Hamaker
Film God

Posts: 2253
From: Lakeport, CA USA
Registered: Jan 2004


 - posted 04-19-2012 05:15 PM      Profile for Justin Hamaker   Author's Homepage   Email Justin Hamaker   Send New Private Message       Edit/Delete Post 
In theory, you don't want to leave the dowser closed with the lamp on for any extended period of time as the heat can damage the dowser. In reality I've found there doesn't seem to be enough heat making it from the lamp to the lens to make this a serious issue - at least not with the NEC NC2000 projectors at my theatre.

The bigger issue we've found with the dowser is that it won't always open on cue as it's supposed to. We leave it open 100% of the time, other than when the projector automatically closes it as part of the lamp on sequence.

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Monte L Fullmer
Film God

Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004


 - posted 04-19-2012 05:39 PM      Profile for Monte L Fullmer   Email Monte L Fullmer   Send New Private Message       Edit/Delete Post 
You'd think with the cost of bulbs and how fast they fade when they get the hours on them that you'd want to turn the bulb off between presentations making the douser issue not an priority issue here .

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Victor Liorentas
Jedi Master Film Handler

Posts: 800
From: london ontario canada
Registered: May 2009


 - posted 04-19-2012 06:16 PM      Profile for Victor Liorentas   Email Victor Liorentas   Send New Private Message       Edit/Delete Post 
But then the ignitions to the bulb increase...

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Antti Nayha
Master Film Handler

Posts: 268
From: Helsinki, Finland
Registered: Oct 2008


 - posted 04-20-2012 02:58 AM      Profile for Antti Nayha   Email Antti Nayha   Send New Private Message       Edit/Delete Post 
According to Ushio, it’s better to turn off the lamp between screenings than to keep it on the whole day:
quote:
Operational Note for Digital Cinema Xenon Lamps:
Based upon our internal research experiments, operation cycles with "On/Off" mode every 2 hours (10 minutes off), delays the generation of lamp flicker by up to 30% when compared to the operation cycle of 11 hours continuous mode.


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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 04-20-2012 04:10 AM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Keep in mind the bulb must FULLY COOL before it is struck again or it is doing quite a bit of damage. That also, from Ushio.

A 10 minute MINIMUM down cycle was their recommendation. If it can't be down for at least 10 minutes, it is far better to leave it burning.

We have already incorporated this cool-down timeframe logic into the DCS as an option that can be enabled at the customer's request.

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Eric Robinson
Jedi Master Film Handler

Posts: 538
From: Santa Rosa, CA
Registered: Jan 2005


 - posted 04-22-2012 10:19 PM      Profile for Eric Robinson   Email Eric Robinson   Send New Private Message       Edit/Delete Post 
I wonder what the effect is on the switching power supply or rectifier regarding continuous or on/off operation.

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Robby Golosino
Film Handler

Posts: 16
From: Davao City, Philippines
Registered: Jun 2011


 - posted 05-04-2012 07:23 PM      Profile for Robby Golosino   Email Robby Golosino   Send New Private Message       Edit/Delete Post 
Well,for me,its better to turn the lamp on and off every screnning for 3 small reasons.1st,to save the life of xenon as long as it can be,2nd xenon is more valuable than the rectifier,3rd is to avoid from being scolded by my superior,lol.

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Dave Macaulay
Film God

Posts: 2321
From: Toronto, Canada
Registered: Apr 2001


 - posted 05-04-2012 08:45 PM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
I guess it depends on the projector. Christie has the dowser before the light processor, so it can probably stay closed with light on forever. Barco and NEC have the dowser after the light processor, just behind the lens. Barco says not to project a test pattern or non-black image on the dowser to avoid damaging it I think. I don't know about NEC. A "black" image passes so little light I can't see it causing trouble with the dowser.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99


 - posted 05-04-2012 10:02 PM      Profile for Randy Stankey   Email Randy Stankey   Send New Private Message       Edit/Delete Post 
As far as leaving lamps burning, my rule of thumb is that one strike of the lamp equals one hour of burning time.

Thus, if the lamp is going to be off for more than an hour, turn it off. Otherwise, it's probably better to burn it.

YMMV.

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Joris Springer
Film Handler

Posts: 83
From: Almere, Flevoland, The Netherlands
Registered: Feb 2007


 - posted 05-10-2012 05:07 PM      Profile for Joris Springer   Email Joris Springer   Send New Private Message       Edit/Delete Post 
Turning the lamp on and off between shows is something I think lamp production companies have probably calculated in when they made the bulbs, I mean why sell lamps that have less than 75% of their guaranteed life span?

But the dowser, I noticed that there was a difference between the DP100/DP90 and the DLP2K/DLP4K series, it seems that there is not really a physical dowser but that it is just projecting black picture. Or the dowser has gotten really quiet [Smile] . I mean on the DP100 and 90 series I could just hear it open and close and now not anymore.

Anyway, we turn of the lamp after every show though when there is a very short time between the movies we keep it now on.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 05-10-2012 06:19 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
I believe the physical douser is part of the DCI spec (would have to spend the time to check and don't feel like it now). That said...every DCinema projector I've worked with has a physical douser, including series 2s...projecting black does not work in mixed venues where multiple projectors are needed (could even be film and digital) because "black" is not really black.

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