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How to fix an LCD projector with a washed-out yellowish image (blue LCD gone bad)

This post gives a little info about how to repair an LCD projector that has a washed-out and yellowing image, which results from the blue LCD panel weakening over time.  I would have to guess that at least 30% of the used projectors on eBay have this annoying problem!

I bought a reconditioned Proxima 9260+ projector three years ago, and it has served me well with a wonderful bright, colorful, and high-contrast image.  I’ve probably used it a total of 800 hours now, and it has been great.  Liking the unit so much, I bought two more of the same kind for really cheap in an eBay auction.  I figured if they were lame then at least I would have parts.  But if they worked OK then it would be an amazingly great deal.  They were advertised as functional, but in need of a lamp replacement.  When they arrived I found out why they were so cheap: one didn’t have a lamp at all, and with a good lamp installed both delivered a really poor washed-out image, yellowed in the middle.  Content on the sides of the screen looked marginally OK.  At the time I was kinda disappointed thinking that perhaps someone had run the units with a really dirty filter, making the inside hot, and roasting the LCD panels.  What was strange though is that both units had about the same hours on them, and both were affected in just about the exact same way.  Didn’t seem likely that two projectors could have been ruined in the exact same way unless it was a manufacturing defect or something.

So this evening I dug in to figure out the problem because I’ve got a pretty big event coming up in two weeks, and I really wanted to get one of my two crappy units prepared as a back-up projector in case my nice one dies during the event.  So I took some time to experiment and see what I could come up with.

Inside an LCD projector there are mirrors that separate out the red, green, and blue components of light, delivering each color to a specific LCD panel.  Then these three panels sorround a prism that combines red, green, and blue from the panels back together to create the resulting image.  After opening the nicer of my two beater units I turned it on and tested each color by shielding the path of the LCDs in sequence.  From this I found that the blue channel was the problem.  It showed detail on the outer edges of the image where there had been less light intensity over time, but in the middle the blue channel didn’t respond at all to a signal, and always let about 30% light through.  Black parts of the image look washed out with a bluish tinge, and parts that should be white turned out yellowish from only getting 30% of the blue channel.  These white areas basically were getting 100% of the red and green, and then blue at about 30%.  This combines to give a yellowish result.  With the projector open and running, I covered up the blue channel, and the red and green portions of the image looked clear and accurate, and blacks were again black.  So I was confident that the problem was either with the blue LCD panel or its polarizer.

Fortunately the LCD panels used in all 3 channels on my projector are exactly the same, with the same ribbon connector and everything.  So I cannibalized a working LCD panel from the green channel on what then became a donor projector, the lamer of my two beater projectors.  After installing it I had to do lots of fine-tuning to get the blue channel in focus and lined up perfectly with the red and green.  Annoying, but I eventually got it close enough to look OK.  All this alignment had to be done with the projector running, loosening and tightening four allen screws that hold in the panel, and nudging it around.  I had made and was projecting a simple cross-hatch pattern in Paint to let me line everything up right.

After dusting out the unit a little and bolting everything back together, it provided a nice, contrasty, colorful image just like my other pristine unit.  I’m delighted with the results.

Curious about why the blue channel was the one that had worn out in both units, I searched on the ‘net a little and found that LCD panels naturally break down in the presence of strong ultraviolet light.  The blue channel from a metal halide bulb happens to deliver tons of ultraviolet, so this is a very common problem with older LCD projectors.  Three years ago TI, the inventor of DLP technology, conducted a study to see if projectors using LCD panels wore down over time.  They used the smallest projectors on the market, with little LCD panels only 0.7 and 0.9 inches diagonal.  These would break down sooner under the same amount of ultraviolet than the larger 1.3″ or 1.8″ panels found in larger conference room type projectors.  Their findings were that the blue LCD panel will always wear down a noticeable amount by 3000 hours of usage, causing that annoying yellowish image.  My units have the 1.3“ panels, which will hopefully last a little longer before throwing in the towel.

Another thing that can happen in a projector is to get blurry magenta spots.  This just means that dust has gotten on the LCD panels, and it can be cleaned out with compressed air.  (Careful to do this only when the unit is off and cold since canned air will cool the panels down quite a bit, and if they’re hot to start with then they could crack.)

Anyway, for anyone else with a Proxima model (really made by Sanyo, and built using Sony LCD panels) it’s fairly straightforward to replace if you have a long 2mm Allen wrench on-hand, and lots of patience when you go to align the image.  Five screws to take off the top cover, and some delicate work with the ribbon cable and LCD panel swap-out.

Maybe my next trick will be to try and refurbish the lamp like some of those other guys out on eBay are doing.  Osram manufactures some good replacement lamps for cheap that would fit the bill.  I think it will be awhile though before I get enough free time to try that out!

This article is part of the GWB Archives. Original Author: Lorin Thwaits

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