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Discussion Starter · #1 ·
Hello, all. I recently bought a used NEC NP-M403H projector and while it typically looks great in bright scenes (first pic), there are whitish “blurs” in darker scenes (second pic, toward top middle on either side of the screensaver “swirl”). Wondering if anyone can tell if the blurs are from lens scratches or does it look like perhaps a bad DMD chip? I have never had a projector with either problem. I thoroughly cleaned everything I could get to without opening up the chassis and sprayed it out with compressed air, so I’m pretty sure it’s not dust/debris.

Thanks for any insights!


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If the dmd was faulty you would see clearly focused pixels stuck on or off. If you see odd shaped white patterns when displaying a black image that usually indicates some fibres/dust on the glass surface of the dmd. If there is something on the dmd you might be able to defocus the lens and get the fibres into clear focus to confirm that's the issue. Easiest to do with just a black image fed to the projector. If you can't focus on it then it's probably elsewhere in the light path.

There's usually a small inspection panel on the optical block where the dmd is which gives you direct access for cleaning either the dmd or back of the main lens. If you do clean the dmd with air use a blower bulb and not something that can leave any residue. You'd need to remove the projector cover to see the optical block just behind the main lens.
 

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Sounds like dust in the optical block. Spraying an assembled projector with compressed air is something you never ever want to do, especially DLP. It almost always forces more dust into the semi sealed optical block. Try the focus trick on a black screen. If that's the case disassembly is required to get access to the DMD. Manufactures under warranty will just replace the whole optical block as it is considered a non serviceable component. There are third parties that will clean it for you but an authorized dealer will change the optical block at a cost generally exceeding the vale of the projector.
 

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Discussion Starter · #4 ·
Wow—great advice! Thank you both so much! I had no idea about compressed air potentially causing problems. I’ll look into your suggestions and let you know how it goes. Much appreciated!
 

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Discussion Starter · #5 ·
Just a followup--the problem is not completely solved but it is significantly better. There were a couple of tiny threads or hairs on the mirror and some dust on the back of the main lens. Gently brushed off those with a swab, reassembled, and the large spots were gone. There are still some (barely) visible white spots if the picture is totally black but I have to actively look for them. I can live with that! Thanks again for all your help!

(There was also a lot of dust in the unit itself plus a couple of dead flies, which could not have been helping much either!) :D
 

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Excellent news! My first projector was a 2nd hand NEC (720p 2004 model) which had white spots on dark scenes. I used a combination of a soft camera blower brush to wipe the glass surface of the dmd chip, as well as a bunched up microfibre cloth for anything more stubborn so that I didn't apply direct finger pressure (to minimise the chance of dragging anything and causing a scratch). For something more severe you could use a drop of isopropyl alcohol on a swab and then wipe away any residue with a microfibre cloth. Basically, anything that's safe for a camera lens.
 

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Side Note: Man, Simon Whistler is even filling up my AVS Forum feed now! Mega Projects, Side Projects, Geographics, Business Blaze... does this guy ever sleep?
 
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