possible to fix white spots / stuck mirrors on a dlp dmd chip? - AVS Forum
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post #1 of 11 Old 10-17-2013, 05:03 PM - Thread Starter
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I do a lot of component level repairs, so I'm comfortable with this. However I'm not sure what approach to take or if it would even be possible.

I've read people talking about it, but no stories yet.

What I plan to do is get ready to buy a new dmd chip during some video watching downtime next week and before I pull the trigger try to fix the current one.

My two options are currently compressed n2o (I've read that the co2 in air duster was bad for some reason), or using a cmos sensor cleaning kit for a high end video camera.

The thing is, are these mirrors really "stuck" or are they actually burned out?

After doing some research, my educated guess combined with experience tells me that it's more likely the electromagnetic filaments on one side of the dmd mirror is burned out rather than the mirror being physically stuck. It seems that heat, which is the root of all other problems in an aging projector, has probably caused these to go over spec and get stuck in a particular position because the actual mirror is no longer physically capable of turning off -- rather than just being stuck in the on position via a piece of dust.

Does anyone have experience with this before I dig in? It should be some interesting research.

Sadly, in my current location, I don't have access to a SEM, or I would just take some pictures of the mirrors to see what's up at the micron level.
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post #2 of 11 Old 10-18-2013, 09:10 AM
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Quote:
Originally Posted by willpower102 View Post

I do a lot of component level repairs, so I'm comfortable with this. However I'm not sure what approach to take or if it would even be possible.

I've read people talking about it, but no stories yet.

What I plan to do is get ready to buy a new dmd chip during some video watching downtime next week and before I pull the trigger try to fix the current one.

My two options are currently compressed n2o (I've read that the co2 in air duster was bad for some reason), or using a cmos sensor cleaning kit for a high end video camera.

The thing is, are these mirrors really "stuck" or are they actually burned out?

After doing some research, my educated guess combined with experience tells me that it's more likely the electromagnetic filaments on one side of the dmd mirror is burned out rather than the mirror being physically stuck. It seems that heat, which is the root of all other problems in an aging projector, has probably caused these to go over spec and get stuck in a particular position because the actual mirror is no longer physically capable of turning off -- rather than just being stuck in the on position via a piece of dust.

Does anyone have experience with this before I dig in? It should be some interesting research.

Sadly, in my current location, I don't have access to a SEM, or I would just take some pictures of the mirrors to see what's up at the micron level.

I believe the only fix is to replace the DMD chip. It there had been dust buildup that was the cause of stuck pixel, then dust should have also collected on the face of the DMD chip which would have been visible in the projected images.

I've replaced a DMD chip on a DLP Rear Projection TV (RPTV) and it took about 90 minutes, being very careful, to complete the repair. The DMD simply drops into a zero insertion force socket similar to a CPU in a PC. Most of my repair time was spend in disassembly and reassembly of the RPTV.



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post #3 of 11 Old 10-18-2013, 09:54 AM
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I have an Optoma HD66 that has a bad DMD chip that started off with 1 white pixel then got worse with white and black pixels all over the screen. The only way to fix the problem is replace the bad DMD chip. There were bad batches of these chips that were produced that were suseptable to heat failure. The DMD chip is sealed so no dust can get inside and doesn't have an effect. The new DMD I have to get for my HD66 is a newer and improved version over the original.

I actually have my HD66 apart right now waiting for the replacement chip. They used a heat pad between the dmd chip and heat sink that supposedly dries up over time and caused some of the failures I've heard, but when I install my new chip I'm going to use artic silver thermal paste instead of the heat pad that comes with the chip
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post #4 of 11 Old 10-18-2013, 12:35 PM
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Quote:
Originally Posted by willpower102 View Post

I do a lot of component level repairs, so I'm comfortable with this. However I'm not sure what approach to take or if it would even be possible.

I've read people talking about it, but no stories yet.

What I plan to do is get ready to buy a new dmd chip during some video watching downtime next week and before I pull the trigger try to fix the current one.

My two options are currently compressed n2o (I've read that the co2 in air duster was bad for some reason), or using a cmos sensor cleaning kit for a high end video camera.

The thing is, are these mirrors really "stuck" or are they actually burned out?

After doing some research, my educated guess combined with experience tells me that it's more likely the electromagnetic filaments on one side of the dmd mirror is burned out rather than the mirror being physically stuck. It seems that heat, which is the root of all other problems in an aging projector, has probably caused these to go over spec and get stuck in a particular position because the actual mirror is no longer physically capable of turning off -- rather than just being stuck in the on position via a piece of dust.

Does anyone have experience with this before I dig in? It should be some interesting research.

Sadly, in my current location, I don't have access to a SEM, or I would just take some pictures of the mirrors to see what's up at the micron level.

There should be a recall on all these optomas with broken dmds.


If you did however use an SEM to take pictures of the stuck mirrors, it would be thread of the year. Easily!!
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post #5 of 11 Old 10-18-2013, 01:39 PM - Thread Starter
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Quote:
Originally Posted by lewis3845 View Post

when I install my new chip I'm going to use artic silver thermal paste instead of the heat pad that comes with the chip
Good advice, I will keep that in mind.

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Originally Posted by Verge2 View Post


If you did however use an SEM to take pictures of the stuck mirrors, it would be thread of the year. Easily!!

I know! biggrin.gif My friend has easy access to one in her lab but she's 15 hours away. frown.gif The closest I came was looking at images of some from the factory spec sheets.
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post #6 of 11 Old 10-19-2013, 09:05 AM
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Quote:
Originally Posted by willpower102 View Post

Good advice, I will keep that in mind.
I know! biggrin.gif My friend has easy access to one in her lab but she's 15 hours away. frown.gif The closest I came was looking at images of some from the factory spec sheets.

Mail her a DMD and a box of chocolates and say "listen woman, I need a solid."



I believe your hypothesis is probably correct. I think it's a heat issue or something. There are some optomas on eBay with thousands of bad mirrors on the screen, no way it could be dust. It's just odd how many optoma hd6X and gametimes you see on eBay with bad DMD's. It's more than just a statistical anomaly, they have bad chips from TI.
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post #7 of 11 Old 10-19-2013, 10:27 AM
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I've heard of people buying new chips and the same thing happens because they used the heat pad again. Then I've heard of people test out the old chip with dead mirrors and replaced the heat pad with artic silver paste or similiar and the chip didn't get worse it stayed the same because if the chip is a bad one the mirrors continually get worse. I also know Optoma finally aknowledeged the problem and the dmd chip is supposed to have a 5 year warranty on it and they did help fix some units even after the warranty period ended so you might want to contact them. Optoma got the most bad chips, but other companies got them also like Acer.
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post #8 of 11 Old 11-06-2013, 03:47 PM - Thread Starter
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Quote:
Originally Posted by lewis3845 View Post

I've heard of people buying new chips and the same thing happens because they used the heat pad again. Then I've heard of people test out the old chip with dead mirrors and replaced the heat pad with artic silver paste or similiar and the chip didn't get worse it stayed the same because if the chip is a bad one the mirrors continually get worse. I also know Optoma finally aknowledeged the problem and the dmd chip is supposed to have a 5 year warranty on it and they did help fix some units even after the warranty period ended so you might want to contact them. Optoma got the most bad chips, but other companies got them also like Acer.

Just got off the phone with optoma and they said that the out of warranty manufacturer replacement for DMD chips on a HD 66 was three years instead of the standard one. My three expired this past July and they aren't willing to replace it.

Guess I'll just throw the DMD chip in it.
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post #9 of 11 Old 02-15-2014, 07:33 AM
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I thought I'd add to this. I just replaced my chip in a rear projection DLP set that was manufactured in 2008. My failure happened perfectly on 1/2 of the screen (left side). Over a period of a month or so it went from one to around 100+. The density also went up from the left and faded out as it got to the center of the screen.

Now that I have the old DLP chip out I can see the traces of the thermal compound only seems to be on 1/2 of the chip. It looks as if the heat sink was only making light contact with one side. The compound on the heat sink looked as if it was still new from the factory. Just like when you get a CPU cooler fresh from the box.

I wonder if it's just something so basic as poor heat sink contact from the factory? Then combine that with a few years of dust build up on the fins. It seems like too basic a problem if that were true.
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post #10 of 11 Old 02-25-2014, 03:03 PM
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I heard that it had something to do with cheap lubricant in the mirrors getting gummy at high temps awhile back. So I have a DLP projector, out of warranty, with a $160 DMD chip cost. At that price, I might as well get a new projector rather than deal with the odds of getting another defective chip.

The end result is whether it's sealed, or sealed. People say pocket camera sensors are sealed but really it's just a rubber gasket with an air hole in it to keep it from fogging (fixed one for dust awhile back). If this is similar, then I can get at the chip and maybe hit it with an (insert chemical) to dissolve the gummy lube and then reapply a new lube. Problems, micro scale and recleaning mirrors 

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post #11 of 11 Old 02-26-2014, 02:54 PM
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Get a new chip. Problem was moisture seepage which screwed up the 'hinges' of the mirrors. Ask you vendor to get you one with the newest date code possible. Late Oct 2011 or newer to be sure.

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