Burnt PBS array - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 02-16-2017, 01:40 PM - Thread Starter
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Burnt PBS array

Hi I have a panasonic PT-AT6000, its got in excess of 10,000 hours on it just starting its forth lamp, I though the third lamp was failing as the brightness had dropped substantially and the hour meter said it was at 4900 hours. Also a red tint appeared at the bottom of the screen and a green tint at the top. (projector is mounted upside down on the ceiling) also the whites appear as cream. I fed it the new lamp and it was only slightly brighter. I proceeded to dismantle the projector thinking it needed a good clean. I took out the prism block, the LCD's looked perfect, next i took out the light guide, the polarizers looked dusty, took the lid off the light guide and found the problem, the PBS array was black in stripes, burnt looking. Also there is what appears to be sticky smoke / vapour coating all the lenses and dichroic mirrors. Question is can i simply remove the pbs array and clean up the optics and re assemble the projector. Can i clean off the burnt material, seems pretty burnt on, tried scratching it off with a screwdriver had little effect. Or bite the bullet and buy a new pbs array. its expensive about 200 euro. Any Ideas the part number is TKGP5494 what does the polarising beam splitter actually do?
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post #2 of 8 Old 02-16-2017, 03:48 PM
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Not sure if this applies to your Panasonic, but here's what Panasonic has to say on their website about the expected lifespan of their panels on another model:

Quote:
The LCD panels and polarizers inside the LCD projector's optical block tend to degrade over time. Their degradation adversely affects image quality. Inorganic materials are used for the LCD panels, and for the polarizers that are prone to degradation, to resist time-related changes in the optical block, therefore achieving a replacement cycle of up to 10,000 hours.
panasonic.net/avc/projector/products/ex16k/features2.html
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post #3 of 8 Old 02-18-2017, 10:00 PM
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10,000 hours!!!
I am close to 500 hours a year and it will take me 20 years to hit that.
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post #4 of 8 Old 02-19-2017, 11:01 AM
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For high use folks who use their projectors as TV replacements 10,000 hours is not that great a lifespan for LCD panels. Consider that some of Epson's newer LCD models have lamp life ratings of up to 10,000 hours in low lamp. The benefit of Epson's low-cost replacement lamps would be a moot point if the LCD panels had to be replaced at the same time.
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post #5 of 8 Old 02-19-2017, 10:56 PM
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I thought 4K-10K was for the organic panels. Regardless, something else would probably fail before the panels I think. Lead free solder.
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post #6 of 8 Old 02-24-2017, 05:49 AM - Thread Starter
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Quote:
Originally Posted by TheronB View Post
I thought 4K-10K was for the organic panels. Regardless, something else would probably fail before the panels I think. Lead free solder.
Well i have a bit more news, have taken the polorizer plate out and got the brightness back but the red tint at the top of the picture and cyan tint at the bottom is still there. If i put up a 100% red , green and blue image it looks as though the red light illuminating the LCD panel has moved up coverage is even across the screen except for the bottom of the image which is much darker the height of which is about 5% of the screen height. The green and blue lights seems to have dropped by a similar amount as the top of the picture when lit with these colours is dark. My guess is that this is caused by the PBS array being damaged or missing. Having found and read the patent for the polorizer plate (pattent number US6154320) it seems not a good idea to run the projector without it as the RGB polorizers in-front of the LCD will over heat, reducing their life span. premature failure of the blue polarizer plate is a common problem in LCD projectors it seems.

The PBS plate actually changes the phase of the wrongly polorized light so that all the light from the bulb is of the correct polarization for use with the LCD's. without the PBS array only 50% of the light is usable and the other 50% is dissipated in the polorizer plates in front of the LCD's heating them up.

None of the panasonic distributors wants to sell me a PBS plate all they will sell me is a complete "analysis block" for around $1200 if i send the projector to them. Not good, thinking about buying a new non pnasonic projector instead perhaps the new dell laser phosphor projector has any one seen it in operation?
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post #7 of 8 Old 04-18-2017, 02:04 PM
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We have the exact same problem with the PT-AH1000E (aka PT-AR100)! The "little brother" of the AT6000.
Because we have two of them we decided to do a test. So we took the PBS plate from the intact projector and put it into the faulty one. And we can confirm that the brightness returned. Not sure yet if the full original brightness (because we didn't compared it one by one) but sure enough to order a new PBS Array from Panasonic for around 250.- bucks.

When we will received the PBS Array will make a one by one comparsion.
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post #8 of 8 Old 11-18-2019, 09:44 PM
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Quote:
Originally Posted by ScopeFan View Post
We have the exact same problem with the PT-AH1000E (aka PT-AR100)! The "little brother" of the AT6000.
Because we have two of them we decided to do a test. So we took the PBS plate from the intact projector and put it into the faulty one. And we can confirm that the brightness returned. Not sure yet if the full original brightness (because we didn't compared it one by one) but sure enough to order a new PBS Array from Panasonic for around 250.- bucks.

When we will received the PBS Array will make a one by one comparsion.
Ever made that comparison?
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