Film-Tech Forum ARCHIVE: NC 900C Blue Dots

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Posted by Sergej Glazar (Member # 10835) on 08-28-2019, 03:23 AM:

Hello
we have a problem with one projector, it keeps showing blue dots on the edge of the picture, we cleaned the lens,and no effect. I think maybe it is on the chip, what should we do, because my boss want to buy a new projector because of that...

Posted by Dave Macaulay (Member # 813) on 08-28-2019, 06:59 AM:

This is likely to be a bad DMD chip with stuck-on blue pixels. Do the spots show in patterns? A full black pattern would show blue spots, full red would have purple spots etc.
I have seen some stuck pixels go away after a few hours of alternating checkerboard but I don't know if NEC include that pattern. I think later versions of the TI software do something to reduce pixel sticking, I don't see it as often as it was 5 years ago (rare even then).
Strong in the USA offer a prism repair service: you get sent a good prism, install it, and send back your original. Changing out the prism should be done by a trained tech. There are some special tools that help a lot.

Posted by Sergej Glazar (Member # 10835) on 08-28-2019, 07:34 AM:

well, the dots appear all the time, even if you only turn on the light, i think that maybe this are not pixels, because the dots are, how should i say, a little out of the picture, if i play the movie, it is near the edge of the movie, and a little on the picture. Becauese the biggest dots are outside the picture and are very visible, on the movie it is not so visible, and when i look the projector from cca 10m, i saw that near the lens,from some small vent opening, the blue light is coming out

Posted by Carsten Kurz (Member # 5396) on 08-28-2019, 08:25 AM:

I guess these blue dots are gone if you close the dowser? Can you supply a photo of the issue?

- Carsten

Posted by Leo Enticknap (Member # 534) on 08-28-2019, 09:52 AM:

Sounds like stuck pixels to me, too.

Maybe try projecting a black/white alternating checkerboard test pattern for a few hours to unstick them?

Posted by Sergej Glazar (Member # 10835) on 08-29-2019, 07:31 AM:

I will post screenshot at saturday, we have this projector for outdoor cinema it is not so visible. So if i understood correctly about these black&white patterns, if i project it for a few hours, it is possible to unstick dots, if it is pixel problem, but it does not look like a pixel to me, i see smeared dots, or are those sticked pixels also

Posted by Mark Gulbrandsen (Member # 72) on 08-29-2019, 07:37 AM:

A clear picture will help answer your questions more than anything. I have also seen dust get into NC-900's prisms and cause spots. So we need to discern which it is.

Mark

Posted by Greg Routenburg (Member # 1742) on 08-29-2019, 11:38 AM:

This sounds to me like what NEC describes as their Blue Star Field DMD failure that was specific to the NC900s. I've had to replace three prisms now with this issue. An engineer at NEC explained to me that there was an issue with UV from the the early lamps that caused issues with that DMD in particular. It's apparently been corrected with the newer lamps but it can manifest itself months or years after. Talk to your local dealer and see if NEC will help you out with it.

Posted by Mark Gulbrandsen (Member # 72) on 08-31-2019, 01:21 PM:

I have not had that happen to any NC-900's yet and I installed a lot of very early units. I did have it happen to the very first MC-3240 4K Light Engines though. In those it was not confined to just the blue pixels. I hvae also had lens mount shift motor leads short out in two units. But thats about it.

Mark

Posted by Sergej Glazar (Member # 10835) on 09-02-2019, 04:28 AM:

Ok, this is it, i put 3 pics together into one, what do you think guys...

Posted by Marcel Birgelen (Member # 6801) on 09-02-2019, 05:48 AM:

Almost definitely a failure of the blue DMD, which means a light engine swap, which might amount to a write-off for a NC 900C if it's out of warranty.

Posted by Mark Gulbrandsen (Member # 72) on 09-02-2019, 08:34 PM:

NC-900 light engines are repairable, but have to be returend to NEC via Moving Images Technology to have that done. Expect it to be gone for quite some time (months). There are no loaner light engines.

Mark

Posted by Sergej Glazar (Member # 10835) on 09-04-2019, 07:53 AM:

Thank you guys for your help, we thought at first that this is only dust, but now we have a bigger problem i see.
Thank you again, this was very helpfull