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» Film-Tech Forum   » Operations   » Digital Cinema Forum   » NEC NC900C prism issue on the blue DMD side, likely dust contamination

   
Author Topic: NEC NC900C prism issue on the blue DMD side, likely dust contamination
Paul Looker
Film Handler

Posts: 81
From: Pittsburgh, PA/United States
Registered: Sep 2009


 - posted 12-22-2015 12:02 PM      Profile for Paul Looker   Email Paul Looker   Send New Private Message       Edit/Delete Post 
prism issue on the blue DMD side, likely dust contamination. That's what NEC support said anyway. I just wanted to hop on here for a second opinion and to see if anyone could tell me if this was something I could take care of myself instead of having a costly service call. Here are the blue and white test patterns where it is visible. Its really hard to see on white but there is an area of yellow discoloration in the red circle.

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And here is a shot of what it looks like on screen while content is running.

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That's a close up shot of the blue discoloration that shows on black picture. The test patterns are running at flat. This is at the bottom of the frame because the feature I grabbed this from is scope. The discoloration is in the same spot flat or scope though.

Any thoughts guys?

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Frank Cox
Phenomenal Film Handler

Posts: 1859
From: Melville Saskatchewan Canada
Registered: Apr 2011


 - posted 12-22-2015 12:36 PM      Profile for Frank Cox   Author's Homepage   Email Frank Cox   Send New Private Message       Edit/Delete Post 
You're sure it isn't a stain on the screen itself?

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Alan Gouger
Master Film Handler

Posts: 472
From: Bradenton, FL, USA
Registered: Jul 2000


 - posted 12-22-2015 12:50 PM      Profile for Alan Gouger   Author's Homepage   Email Alan Gouger   Send New Private Message       Edit/Delete Post 
The % of blue combined with a larger % of Red and Green = white.
It makes sense it would be harder to see on anything but Blue background. Judging by the photos most likely some form of contamination on the Blue DMD.
The new 1201 Blue Phosphor ( revamped NC1100L laser ) has a sealed light engine. Going forward if that becomes common that should minimize the risk of contamination.
In your case this may require a service call by a qualified technician.

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Paul Looker
Film Handler

Posts: 81
From: Pittsburgh, PA/United States
Registered: Sep 2009


 - posted 12-22-2015 03:12 PM      Profile for Paul Looker   Email Paul Looker   Send New Private Message       Edit/Delete Post 
Definitely not a stain on the screen. Does anyone know of any technicians in the Pittsburgh area?

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16057
From: Bountiful, Utah
Registered: Jun 99


 - posted 12-23-2015 06:48 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Also check the front lens element for a glob of stuff and the rear element if you feel comfortable pulling the lens. It's a twist lock affair. I have not had any issues with NC-900's light engines being contaminated and I've installed just over thirty of them. I have had a couple NC-2000's become contaminated due to Strongs crappy filters. It is possible for a competent technician to clean some of the prism on site. Just beware that you get a technician that's competent with optical cleaning.

Mark

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11982
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-24-2015 03:50 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
I've now seen the inside of an NC900 with some hours on it. A LOT of dirt flies around in there...even with NEC's filters. It is quite easy to believe that some dirt has made it to the prism area (and/or light pipe).

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Marco Giustini
Film God

Posts: 2535
From: Reading, UK
Registered: Nov 2007


 - posted 12-24-2015 09:36 AM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
To be fair the cleanest projectors are the Christie's. It's a shame, it wouldn't take much to improve Barco's and NEC's.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11982
From: Annapolis, MD
Registered: Dec 1999


 - posted 12-24-2015 10:50 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
It all depends on Christie. The CP2208-CP2215 isn't the cleanest projector in the world. Christie also doesn't filter their lamp compartment on any of their projectors.

Barco filters some things with a wire mesh filter that keep boulders out but not fine dirt at all. They also let the LPS fend for themselves and make the inlets on the "C" series hard to reach. They also have a fan that blows on the back of the lamphouse/Lamp Info Module ("C" series) that gets unfiltered air.

What air you start with also has a great effect on the outcome.

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Marco Giustini
Film God

Posts: 2535
From: Reading, UK
Registered: Nov 2007


 - posted 12-24-2015 12:37 PM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
the 2210/2215 should have a sealed light engine, maybe that's why filtration is reduced.

I agree with the booth air: in my cinema I'd have filtered air in the first place. As you say it would make a massive difference. It used to be a massive difference on 35mm!

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Paul Looker
Film Handler

Posts: 81
From: Pittsburgh, PA/United States
Registered: Sep 2009


 - posted 12-25-2015 08:14 PM      Profile for Paul Looker   Email Paul Looker   Send New Private Message       Edit/Delete Post 
Mark, I feel comfortable pulling the lens if I could get a step by step instruction for someone (me) that has a hard time reading manuals. I saw it needs to be centered. I'm not 100% on how the lens comes out but I didn't even really get that far because read and read I couldn't figure out where exactly it was telling me the control to center it was.

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Marco Giustini
Film God

Posts: 2535
From: Reading, UK
Registered: Nov 2007


 - posted 12-26-2015 05:50 AM      Profile for Marco Giustini   Email Marco Giustini   Send New Private Message       Edit/Delete Post 
I doubt that comes from behind the lens but it's indeed something to try.

Another thing you can try is this: place a piece of white paper in front of the lens, say 1-2 metres away. Now zoom the lens in either directions till you can focus the dirt on the sheet. You should be able to see that spec of dust very clearly.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16057
From: Bountiful, Utah
Registered: Jun 99


 - posted 12-28-2015 10:24 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Briefly, There is a lens lock lever you hold and then the lens twists about 33 degrees to pull straight out...

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