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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » Lamp question (Page 1)

 
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Author Topic: Lamp question
Gronw Roberts
Film Handler

Posts: 54
From: Y Felinheli, Gwynedd, Wales
Registered: Oct 2015


 - posted 12-19-2017 10:31 AM      Profile for Gronw Roberts   Email Gronw Roberts   Send New Private Message       Edit/Delete Post 
I was told recently that a lamp needs to cool down before being re ignited otherwise it can cause problems. Is this true? I ask because the gap between playlist for the new Star Wars are short (4 screenings a day), the shortest being 4 mins. The lamp failed to ignite yesterday (my day off so I didn't see it) although the gap was 14 mins in that instance which seems like more than enough time.

We have had our igniter and power supply replaced recently (NEC NC2000C) because the lamp on command wasn't working all the time and it's been fine since. It seemed to be more problematic when the gaps between playlist were short. If I can get my laptop to work I'll pull the logs to see what happened, there's no one else around today that was here when it happened to talk with me about it.

At the moment I've taken out the lamp on/off commands from the playlist and added them to the schedule instead, the lamps on all day now but the gaps between playlists are so short I'm not losing too much lamp hours at all.

So can re igniting too quickly cause problems? I can't be here all the time so I need to make sure the way I'm automating has the best chance of success.

Thanks.

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Frank Cox
Phenomenal Film Handler

Posts: 1974
From: Melville Saskatchewan Canada
Registered: Apr 2011


 - posted 12-19-2017 10:54 AM      Profile for Frank Cox   Author's Homepage   Email Frank Cox   Send New Private Message       Edit/Delete Post 
It's always been my understanding that if the gap between shows is less than 20 minutes then you should leave the lamp on. And striking a lamp before at least ten minutes of cool-off time is really hard on it.

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Gronw Roberts
Film Handler

Posts: 54
From: Y Felinheli, Gwynedd, Wales
Registered: Oct 2015


 - posted 12-19-2017 11:13 AM      Profile for Gronw Roberts   Email Gronw Roberts   Send New Private Message       Edit/Delete Post 
Thanks Frank. I'll make sure to keep that in mind from now on.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12209
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-19-2017 12:38 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
The current recommendation from the likes of Ushio is a 10-minute off period per show but if there is less than 10-minutes, leave the lamp lit.

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Gronw Roberts
Film Handler

Posts: 54
From: Y Felinheli, Gwynedd, Wales
Registered: Oct 2015


 - posted 12-19-2017 12:45 PM      Profile for Gronw Roberts   Email Gronw Roberts   Send New Private Message       Edit/Delete Post 
Thanks Steve.

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Jack Ondracek
Film God

Posts: 2308
From: Port Orchard, WA, USA
Registered: Oct 2002


 - posted 12-19-2017 01:24 PM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
Our drive-in runs lamps that range in size from 4,000 to 6,500 watts. We run them for roughly 4.5 hours a day, once you add intermission and the time we turn them on before we start.

We start them manually at the beginning of the show, and let the automation shut them down at the end of our double features.

I've got no science to back up our habit. It just seemed dumb to shut them down, just to start them back up again. We also had some early trouble, re-lighting hot bulbs, but a software update fixed that some time ago.

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Carsten Kurz
Film God

Posts: 3777
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 12-19-2017 04:28 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Gronw - while you might reason about 10min vs 15min in general, I think when you have such a tight ongoing schedule like currently, you should not use automatic lamp off. Yes, the bulb may add on some few hours like this, but lamps clearly also age with ignitions.

- Carsten

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12209
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-20-2017 06:56 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Carsten, again, Ushio is showing that a 10-minute off period, per show improves lamp life/stability.

From their "Spec sheet":

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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Gordon McLeod
Film God

Posts: 9460
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 12-20-2017 09:52 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
That is a very poor design requirement to require a cool down each 2 hrs
Almost all theatres i deal with run there lamps all day as adverts start as soon as the feature ends and there is always something on the screen

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Jack Ondracek
Film God

Posts: 2308
From: Port Orchard, WA, USA
Registered: Oct 2002


 - posted 12-20-2017 11:25 AM      Profile for Jack Ondracek   Author's Homepage   Email Jack Ondracek   Send New Private Message       Edit/Delete Post 
Guess that brings up another question. Is the onset of flickering a common problem with digital xenon? Seems that, considering the dramatically shortened warranties these things come with, you barely have time to tint the envelope, much less degrade the anode.

At my place, I get full warranty out of my 4kW bulbs and flicker, to the extent you can see it, has never been a factor... maybe as much because I never get close to 4k with them as anything else. I can take my 6.5k bulbs to warranty, but I run them hard and the falloff is noticeable enough that I don't get too much past 1/2 life out of them.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12209
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-20-2017 01:56 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Gordon. It isn't so much a design REQUIREMENT as a fact of xenon lamps and their nature. They FOUND (not designed in) that a 10-minute cool down between 2-hour feature improved lamp stability.

They don't require nor deny warranty because you can't prove a cool down period. Depending on the schedule, we too have lamps that never turn off during the day. On our TCC systems, we set the threshold to 10-minutes. If there is a 10-minute or more gap, the lamp goes off. Any shorter, the lamp stays on. We've had no issues getting warranty out of them.

As for lamp life (warranted) in DCinema versus Film Cinema, really, the lamp life is as high or greater, in most cases. 2K cinema lamps were 2000-2400 hours, DCinema they are 2400-3200 hours. 1.6K lamps were 1500-1800-hours, DCinema are 3000-hours. 4K lamps were 900-1000 hours, DCinema are 1000-1300 hours. 6K lamps were 500-hours DCinema are 500-800 hours.

Now, the lamps are not priced exactly the same but they also don't put out the same light either, with DCinema typically 20-50% brighter than their film counterparts.

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Carsten Kurz
Film God

Posts: 3777
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 12-20-2017 05:22 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Steve - he says that occasionally they had only 4min between shows and still shutdown the lamps because that is in tbeir playlists. I don't know how they organize their schedules and playlists, but once it becomes so tight, it's useless to save a few minutes run time per day by risking hot strikes or strike failures. They will only have that issue for those few weeks they play SW8 - so I would simply stop shutting down the lamps beetween these shows. It's just not worth it. They may return to their normal dealing once their schedules normalize as well. Another option would be to just lower the lamp current between tight shows. We do this on our two UHP systems, and it seems to increase bulb life noticeably. That said, UHP really dislike ignitions.

- Carsten

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Gronw Roberts
Film Handler

Posts: 54
From: Y Felinheli, Gwynedd, Wales
Registered: Oct 2015


 - posted 01-06-2018 08:29 AM      Profile for Gronw Roberts   Email Gronw Roberts   Send New Private Message       Edit/Delete Post 
Thanks all. I'm keeping the lamp on all day for the duration of Star Wars 8 and will automate future playists accordingly taking in to consideration how much time there is between films.

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Peter Hall
Master Film Handler

Posts: 307
From: London, UK
Registered: Dec 2000


 - posted 01-06-2018 10:28 AM      Profile for Peter Hall   Author's Homepage   Email Peter Hall   Send New Private Message       Edit/Delete Post 
I may be wrong but I'd usually associate flicker with worn electrodes on the lamp - interesting that the drive in (with I guess a slightly upwards rake) doesn't get flicker issues. Where we have seen uneven wear on the points, we have implemented a 1/3 rotate every 1/4 lamp life and this usually exceeds warranty hours. With 35mm and extreme rakes, sometimes an additional arc magnet helped. Interestingly with Digital, we seldom get flicker on Barco projectors, where the lamp is always horizontal. Does anyone remember the vertical Cinemecannica xenon lamphouses ? - the lamps lasted forever but they gave appalling light output..

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12209
From: Annapolis, MD
Registered: Dec 1999


 - posted 01-06-2018 06:20 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
On the Barco DPxK-32B, there is a magnet in the lamphouse near the bottom) that helps with arc stabilization. A "feature" of both Barco and NEC is that regardless of projector tilt, the lamp stays horizontal because it is mounted transversely.

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