Mitsubishi TV Salt and Pepper on screen

I saw a Large Mitsubishi TV, not quite flat panel just a little round out on rear at bottom center. I think an age clue. The entire screen had randomly scattered but stationary black and white dots. Maybe about the size of the comma on your keyboard or just a little larger. On one scene with a grey screen, and the Black and white spots, it looked like one of the garage floors painted grey with the specks thrown on it. Almost exactly like that.

Any idea what could could this strange defect?

Mikek

Reply to
amdx
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Simple: bad dmd imager. Texas Instruments had a bad run that affected an en tire run from Mitsu, Toshiba, and Samsung sometime around 2007 IIRC. Samsu ng is telling people tough shit, not sure about Toshiba, but Mitsu (with en ough crying), will ship the dmd chip to a servicer who will install it and clean the optics, you pay the labor. This info was accurate as far as Marc h 1st this year.

Other than the TI chip, this model Mitsu is trouble free other than needing a new lamp every 6K hours or so.

Reply to
John-Del

Very good, I had an auto seat recovered at an upholstery shop, It was the TV in their office. I ask about it, he said when he bought it ($100), it only had maybe ten spots scattered around the screen, and it just kept getting worse. It's been 20 years since I was involved in the repair business, I basically missed the flat screen change over. So I had to google dmd imager.

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I printed your info and the wiki info and gave it to the upholstery shop owner. Nice guy, I dropped my seat cover off at about noon, he had it done at 4:00 and I had it back on the seat and the seat back in the van by

5:00. If I had known it was that easy, I wouldn't have been driving the van with a big hole in the drivers seat for three years. Thanks, Mikek
Reply to
amdx

DLPs are probably the worst TVs to use in a commercial application as they usually run all day. OEM lamps are good for 6000 hours on average, web sou rced knock offs about 1000 hours.

Once the DMD starts to die, the rash expands fairly rapidly. I changed one last month where the entire picture was covered with sparkles. Between th e cost of the DMD image chip and the lamp usage, I would not recommend a re pair on this TV that runs this many hours.

I have several customers with "institutional" use TVs (doctors, mechanics e tc.) and I've located CRT TVs for them to use in their waiting areas. A go od CRT TV will run almost indefinitely and care little how many hours they run. A gave a friend of mine (muffler shop) an old 80s RCA CTC130 25" for his waiting room and it's been running every day for almost 15 years straig ht. Kids have thrown toys at the picture tube face, scratched the tube and damaged the front control buttons, but it works by remote so no big deal. I saw it last month and the CRT is starting to show some beam scatter in th e corners, so the tube is finally getting soft, but it's certainly usable.

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n entire run from Mitsu, Toshiba, and Samsung sometime around 2007 IIRC. S amsung is telling people tough shit, not sure about Toshiba, but Mitsu (wit h enough crying), will ship the dmd chip to a servicer who will install it and clean the optics, you pay the labor. This info was accurate as far as March 1st this year.

ding a new lamp every 6K hours or so.

Reply to
John-Del

When you say "salt and pepper", do you mean white noise that a screen shows when it has no specific signal? Like this?

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Reply to
mogulah

Nope.

"The entire screen had randomly scattered but stationary black and white dots. Maybe about the size of the comma on your keyboard or just a little larger. On one scene with a grey screen, and the Black and white spots, it looked like one of the garage floors painted grey with the specks thrown on it. Almost exactly like that."

Mikek

Reply to
amdx

The "salt and pepper" that you are describing is a random smattering of stuck pixels on your DLP chip. Some of them are stuck on (white) and some are stuck off (black). I had this exact same failure on my Samsung DLP television. It started with just a few stuck pixels, but over time grew to much more.

My samsung DLP has an LED backlight, so I deemed it worthy to replace the DLP chip. I bought it from shopjimmy via Amazon. The price was about $200. It was pretty easy to replace - There are a lot of instructions available on the web for various models. After replacing the chip, the image on screen is just a teeny bit crooked, but I can live with it. It was too much trouble to try to open the set and manually re-adjust the alignment. There doesn't seem to be ANY kind of electronic adjustment to correct this.

Reply to
Matthew Fries

Like this? ::

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ShopJimmy has DLPs available for most back-projection TVs.

Good luck.

Reply to
DaveC

FYI, the white dots are pixel mirrors that are stuck "on" (reflecting light to the screen) and the black ones are stuck "off" (not reflecting light to the screen).

Reply to
DaveC

So is it something physical making the mirrors stick or failed electronics? With the 10 or so DLP projectors I've played with , all dumpster-fodder, always ps failure or absent, presumably failed lamps, not a single stuck pixel have I seen.

Reply to
N_Cook

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The stuck pixel phenomenon only affected a specific run from TI, somewhere in the 2007 range IIRC. I have an 06 Mitsubishi 1080P native resolution pro jector and this earlier model never has this problem. Later Mitsus don't e ither.

As for the failure mode, I'm going to presume it's mechanical. I replaced o ne a few weeks ago and it was loaded with bad pixels that the DMD chip had a sandblasted appearance instead of what normally looks like a perfectly re flective 16X9 mirror. I've got some scrapped going back two years and the s tuck pixels are still visible by eye under magnification.

I've played around with these using heat and mechanical vibration and there has never been any effect on them. They have a torsion hinge in them and I'm guessing that they might be some sort of flexible elastomer that's fail ing with heat and repeated cycles.

Reply to
John-Del

The torsion hinge is pure aluminum, and probably thinner than the mirrors. they build this all on a metal layer up above the chip circuitry, and then etch out the platform under the mirrors, freeing them. They rock back and forth under electrostatic force from pads on the chip surface under the corners of the mirror.

The whole general scheme is in some docs published by TI a long time ago. VERY fascinating stuff to read, some of the earliest MEMS work. They apparently have some kind of lube layer that is supposed to keep the mirrors from sticking, and it breaks down under UV bombardment.

The mirrors are typically 11 um across, so you would have to hit the thing with a bullet to produce much acceleration to the mirrors. No way can you shock the mirrors free once they have stuck.

Jon

Reply to
Jon Elson

Thanks Jon. Makes more sense when you think about it. At the dimensions that we are talking about, etching out makes more sense than attempting to assemble with a dissimilar material for the torsion hinge. It's amazing these things actually work.

Reply to
John-Del

Yes, but much, much, worse, the whole screen area is covered. Mikek

Reply to
amdx

etching out makes more sense than attempting to assemble with a dissimilar material for the torsion hinge. It's amazing these things actually work.

Thanks for all the info guys, I'll print it and give it to him, then he can decide if the tv is worth another $200, and if he can even do it.

Reply to
amdx

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