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Discussion Starter · #1 ·
I'm relatively new to home theater and, after spending time on this forum I recently purchased a Sanyo XP21 LCD projector. My choice was dictated by the ambient light in my family room and many of the comments from this forum. Over all I am quite please with the picture - whites, blacks and colors are great and screen door is not much of an issue.


That said, within 2 days of getting my projector it developed a dust spot (large green blob just left of center) that was easily visable on all dark material. Then, about two weeks later the unit started shutting down spontaneously. Sanyo, to their credit, paid to have it shipped back and, since its return, dust in gone and no more power problems.


Now, however, and again within 2 days of getting the projector back, it developed what I assume is a single dead pixel (single pixel that is always green and easily visable in any dark material). I was of course disapointed, and then about a week later another single green pixel developed about 6 inches from the first. Needless to say, I find them quite noticable and very distracting, particularly since I have only had the projector about 4 months.


So here are my questions:


1. At the prices of these units, I expcected near perfection, but that has not been the case. Is my experience different from most? Do most or all LCD projectors develop dead pixels and dust spots? As anyone done a poll on this question?


2. What are my options? How may pixels must go bad before I should raise he?? with Sanyo? Do dead pixels come back, or can they be reserected?


3. Is there a difference between LCD, DLP and D-ILA projectors in terms of dead pixels and dust problems?


Any and all comments and experiences would be greatly appreciated!!


SFC
 

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The green spots you describe may be more dust,it is unusual for pixels to die after initial manufacture.I had a Sharp projector a few years back with what I thought were dead pixels (green spots) but they miraculously dissappeared when the panel was cleaned.Dead pixels are REALLY bright.I would't buy another lcd projector for fear of dead pixels.DLP projectors suffer far less from this problem and seem to be more easily exchanged.
 

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Discussion Starter · #3 ·
Thanks meva!


I was certainly curious that my pixels were green, just like the earlier (and much larger) dust spot. If it is true that dead pixels are bright (white, colored?), then what I have may just be dust (though it is just two single but separate pixels?). That gives me some hope that a simple cleaning will remove them. Any other possibilities, given their small size?


SFC
 

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SFC:


I'm about to purchase this projector so I would be very interested to know that the latest "green spots" are dust and not dead pixels.


Thanks.


Dan
 

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Dead pixels don't have to be bright. It depends what color pixel is dead. For example, I have what I beleive is a dead green pixel on my DILA. I does not show up at all unless you are looking at a grey or light blue screen, in which case it comes out as purple. On a green screen, which is pretty rare in a movie unless it's about golf, it comes out black. Perhaps a pixel that is stuck on all the time would be bright, i.e., it would be bright green, red or blue.


One way to check if it is dust is to defocus and try to get the dust blob (it that is what it is) in focus. If it is dust, it will not be on the same focal plane, and when the projector is out of focus, the dust will appear focused and have sharp edges. (And you will also probably see smaller dust particles that you didn't know were there.) If it's bad pixels, they will go out of focus when the projector is out of focus. Also, try several of the color fields on Avia. If it's a dead pixel or stuck on pixel, it will tend to show or not show depending on the background color.
 

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Discussion Starter · #6 ·
Thanks All!


I will try the focusing experiments within the next few days.


To DanHouck - I clearly had a dust spot when I first set up my projector (it was difuse and covered perhaps a 20 to 30 pixel diameter area), which went away when the unit was cleaned. What I appear to have now are single green pixels (and thus much smaller than what I saw previiously) which are only visable on dark fields. In fact, last night I did not see them at all (they may be gone?). I will comment more in a day or so. Otherwise, I am quite pleased with the projector and it's image. As background, I am using a PC to drive the projector, as I found this to be significantly better than a direct feed from my 480i DVD player. Others I know have also had great success with a DVD player and a QuadScan.


SFC
 

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Hey SFC,

the problems that you have encountered with your SANYO LCD projector are exactly one of the reasons why i decided to wait to purchase a new front-projector, which i am pretty sure will be a DLP unit, and i am willing to wait as long as it takes untill i am absolutely sure that DLP technology has caught up to CRT's in contrast and resolution...and i would wager to say that we are almost there!

insofar as "dead pixels", here is what Scott, over at TI, the manufacturer of DLP's, had to say:

"DMD pixels do not die like LCD pixels do.usually the LCD pixel material breaks down forming charge-carrying ions that cause the pixel to short out. because such chemistry does not exist for DLP's, these problems do not occur."

i could see similar problems to the ones you experienced with "dead pixels" on the screen of my portable DVD player, which came with several defective pixels, some blue, some red and some green, and the interesting part is that i can only see each one of them depending on the background color that happens to be onscreen around the defective pixel!

in other words, if the main color onscreen happens to be a blue sky, then i can clearly see the green "dead" pixel, but not the blue "dead" pixel, which only shows its face in a yellow background, and so on....!!!

regards, MCaugusto
 

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Gee... I wonder why I have this dead pixel on my LT150 then if they're not supposed to happen on DLPs...


------------------

/frode
 

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hey Frode,

it would seem to me that what you described as a "dead pixel" on your DLP should be more appropriately called a "stuck DMD"...in other words, one of the hundreds of thousands of the "DIGITAL MICROMIRROR DEVICE" in the DLP assembly stopped going into the ON/OFF stage like they were built to do for a very extended period of time.

i might be wrong on this, but i think i read somewhere that DMD's have been tested by TI to last past 20 years of average use, which i would say is pretty good performance, don't you think so?

i wonder how many more owners of DLP's have encountered the same problem as you have,and, as an aside, how prevalent is this same problem for owners of brand-new LCD's projectors, as well as after 1.000 hours of use...???

regards, MCaugusto
 

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If you're trying to avoid dust supposedly some of the Seleco units (e.g., 200M and 250M) have a sealed optical assembly. This is obviously very attractive.
 

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Discussion Starter · #11 ·
Hi All!


Thought I should follow-up since I started this thread!


I went back and tried to focus on the 'spots' and, sure enough, they do not appear to focus in the same plane as the pixels. In fact, they appear to be just about one pixel in size but irregularly shaped. Thus, I'm pretty convinced these are NOT dead pixels.


Does this suggest that they are small dust particles? Relative to what I saw previously (something covering many pixels), these are quite small. Any again, why green? If you get dust or other particles in the system, is there a logical reason why they would appear green (I HAVE looked for other colored pixels and do not see any)?
 
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