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Discussion Starter · #1 ·
I know that it is related to blown transistors, or something of that sort. Why I don't understand, is because the computer I am using has a CPU with millions of transistors, a video card with the same number, and can use them for years.


Why, then, do LCD's go bad? I could understand if DLP's had bad pixels becasue they are motor based, but they seem to be even better than LCDs


Any insight?
 

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has a lot to do with it. Think of it as defects per unit area. The type of "defects" that can cause problems with semiconductors are numerous, but it only takes one to create the malfunction.


One of the pricing functions for semiconductors has to do with the die size since it essentially governs the number of units per slice of silicon that can be produced. The bigger the die the smaller the number of functional die per slice. That is to say a defective one is a greater percentage of the total so the "yield" drops.


With traditional semiconductor technology "die shrinks" are the norm. Meaning that the next generation of a part or evolution of a process allows for the individual transistors to become smaller thereby increasing the "yield" of functional units per slice. This drops the cost.


With LCD panels you can't just make them arbitrarily smaller due to the intended application. The consensus then is to allow a certain number/grouping of defects to still be considered OK. Otherwise the price would truly be unaffordable.


At least this is what I've been led to believe.
 

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As far as the DLP is concerned, beats me. I do believe that since it is what is called a MEMS, or Micro EltroMechanical System taht the processing is different than that for LCD. Also the hinge mechanism for the DLP mirror is only a single crystal lattice thick and apparently does not suffer from work hardening so they have a fantastic lifetime.


There are some good white papers at dlp.com


I probably got most of this backwards so pay it no mind.



edit--(few atoms --> single xtal lattice)
 

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after it has been working is a different story. The panel in a PJ is subjected to a lot of heat due to the bulb. I think this plays the major role in the failure. A transistor that is marginal to begin with will exhibit the failure first at accelerated temperature.


Really need the semiconductor physics boys to weigh in here. I am truly outta my league.
 

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DLP's are not cheap panels - but most DLP machines are one-chip machines with color wheels, while LCD projectors are triple-chip machines with literally three times the number of pixels as single-panel designs. I was shocked to see a bright cyan pixel stuck on in the $10K DLP RPTV at my local home theater store.


I think the stuck pixels are just as common on both the technologies, and are related primarily to masking defects during panel fabrication. The difference is, you can scrap the single-chip panel and replace it, whereas by the time you know about an LCD defect, the three-chip panel has been assembled into an expensive optical assembly with polarizers and beam splitters - and a lot of monetary pain if you scrap it.


One difference is that DLPs are mechanical devices - in theory the micro-mirrors would begin to fail as the panel ages, because they are moving parts. LCDs have no moving parts other than simple assemblies like fans - I would expect them to remain stable and not develope pixel flaws over time, unlike DLPs.


I don't think there are any DLPs with enough hours on them to know if there is any truth to my theory. In a few years we should know.


Gary
 

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Discussion Starter · #7 ·
CPU's still deal with heat issues, and I am sure they outnumber the number of transisters on an LCD panel..even 3x.


Sony, I remember with the 400Q, had a 3 transister/pixel system...and even that still had dead pixels. So..whats the deal?
 

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David,

As jamin has mentioned the size of the die has a lot to do with yield and reliability. The LCD panels are pretty large compared to a CPU. Smaller panels would be better but there are issues in trying to focus and shine an extremely bright lamp through a very small LCD panel. DLP and LCOS have similar restrictions on size. LCOS technology can make smaller dies than the current lamp technology can drive. As lamp technology gets better, die size will decrease and that means increased yields, better reliability, and lower cost.


--sdc
 

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Discussion Starter · #9 ·
For the gentleman who mentioned seeing a stuck cyan pixel on RPTV DLP? Was this a 3 chip unit? If it was a one chip unit, than it is impossible for the pixel to have only one colour,as it is being flashed RGB. Correct?
 

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David: I might be totally wrong (and I am probably wrong in some respect), But I must disagree with your conclusion "than it is impossible for the pixel to have only one colour". If that was true then all films you see on the DLW would only have three colours (the number on the color wheel). In a sense you should see three colours, but it is spinning fast enough that all the colours get mixed and you see one colour (the rainbow effect is the opposite of this). So all that would mean (if it is a single DLP unit) is that the weal is not balanced and has a natural tendency towards cyan.
 

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David,

I'm not actually sure if the Panasonic Tau model PT-52DL10 is a single-chip or triple chip DLP. It's a stunning model that has 52" diagonal 16:9 aspect ratio, and the native resolution is 1280X720. The best feature is it has a very wide viewing angle compared to CRT RPTVs.


The one I saw had the optional stand and was further displayed on a 12" high carpeted pedastle, which put the stuck pixel (upper right corner abot 3" down and 4" from the edge) right at eye height for me. The color was bright Cyan, and it was visible on any darker background - but I couldn't see it against white background. The picture was otherwise tweeked to perfection (it's a good dealer and store) and finely focused. The bright, colorfull, rectangular shaped pixel was very intrusive and as a result the set was (in my opinion) absolutely unacceptable.


The most shocking part was the MSRP of $12,999.97 - although this was a floor sample marked down to $9999, and I've seen them on the web for $8270. Stuck pixels are marginally acceptable on a $3000 projector, when you spend $8000 or more, I think you have a right to expect perfection.


Gary
 

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I had the opportunity to see the Panasonic at "Great Indoors" in Chino Hills. There was a comparison loop that played one after another comparisons of flowers along with other scenes of "extrodinance". The flower comparison was AWESOME. My friend and his wife who saw it had the OMG factor. They are NOT techies. I am! I saw it and was VERY impressed. It kicked ass on anything I'd EVER seen. I'm dying to get the new pioneer elite, but I think this thing, although it COSTS a buttload, was the BEST I'd ever seen. Would someone please comment on it? My main question is; does this thing have 1080i capability? I've heard it is only capable of 720P. Let me know. Obviously, it's not worth $10,000. But I think the technology cost should come down.
 
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