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Unwanted blue lights

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4 replies to this topic

#1 of 5 OFFLINE   Scott Thomas

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Posted September 17 2007 - 03:27 AM

I've my Sony VPL-HS3 front end projector for about 2 years, about a month ago there was a streak of blue on the upper left hand corner. gradually, more and more of blue has been showing up on my screen mostly on the both and the top of the screen, the rest of the screen is fine and brightness and color is still tip top. At first I thought the lamp was burning out and I was just reluctant to replacing it. However this morning, I did replace the lamp with a fresh one and all the problems are still there. Could be a problem with the projector itself? The wiring? The Screen?

#2 of 5 OFFLINE   homthtr


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Posted September 17 2007 - 10:27 AM

Are you getting the same results from all video sources? DVD,Cable/Satellite,VCR or any other Video source you have connected?

Is all your video connected through an A/V receiver? (in other words are you using the same input on the projector and switching sources through your receiver)

I would NOT suspect the wiring given your description of the problem.Posted Image

#3 of 5 OFFLINE   Leo Kerr

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Posted September 17 2007 - 01:02 PM

This is the fatal flaw of transmissive-LCD-based projectors, and this sort of problem is your polarizer.

The optical block has all sorts of beam splitters, polarizers, LCD panels, mirrors, filters, et cetera.

In general, here's what's supposed to happen, and then I'll explain what is happening.

Light from the lamp goes through some sort of integrator/beam smoother, an infrared filter, and then is "pulled" into the optical block by an array of dichroic reflectors and prisms. Dichroic reflectors are metal-film-on-glass panels that "filter" the beam by selective reflection, rather than by absorption. These filters generate the three fundamentals, red, green, and blue.

These three beams are then routed through polarizers, which selectively orient the wave-motion of the light. This is, unfortunately, a destructive filter, in that the light not going in the right orientation is converted into heat. The polarized light then proceeds to the imaging panel. LCD 'cells' work by rotating a liquid crystal material that, oddly enough, polarizes light. To make a cell 'dark,' the orientation of the liquid crystal is cross to the polarization of the first filter. "Bright" is orienting the light in the same direction, and "medium" is some position in between.

Colored, modulated light is then recombined via prisms and mirrors, and is sent on out the lens to the screen.

Now, in your case, one of your polarizers is beginning to... depolarize.

You may be able to get replacement polarizers. You may have to end up replacing the optical block (the entire "guts" of the unit.) Or you may find it that when it's beyond annoying, it's easiest and cheapest to replace the projector.

Heat is the enemy here, and there's not much that can be done about it. Some LCD projectors won't honor warrantees on optical blocks if the projector is "abuse" by running it more than X hours at a time; we had some at work where they wanted four hours off between every two hours on. Not something that we were going to do. Other projectors have extensive heat-controls built in - fans and the like, better sinks, et cetera. Some also have an 'eco-mode' which, in addition to stretching the lamp-life, also takes longer to build up the heat in the block.

Given the life of two years, I'd be annoyed with the unit for premature failure unless you tend to run it for a whole bunch of hours at a shot. I tend to do one movie a night on mine, and haven't had any troubles in that direction yet.

For a future, replacement projector, the only way around this particular issue is DLP or, to some extent, D-ILA/LCoS. I've heard, however, that they can develop image-retention issues, but I don't know how reliable that source is. DLP, of course, has the dread rainbow-effect.

In watching three different locations do this, with several different (serial number) units, I also wonder if some units have better heat-control with different orientations. We had two ceiling mount and one table-mount. Given the different conditions, we had very different lamp-lives, as well as polarizer lives. In our case, ceiling mounted projectors had better polarizer lives, while the table-mount had a much better lamp-life.

Oh, dear. What started as a simple response... grew.

Leo Kerr

#4 of 5 OFFLINE   Scott Thomas

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Posted September 18 2007 - 12:56 AM

The Technical jargon you just described went right over my head, but from it sounds like the unit is being burned from the inside due to do so much use. My project is a ceiling mount. There are some days where I only watch a couple hours in the morning and some hours after work. however, on other days I can spend up to 8-10 hours watching TV. I've been playing my games a lot lately, and with Halo 3 coming its not going to slow down any time soon.

#5 of 5 OFFLINE   Chris Dias

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Posted September 18 2007 - 03:26 AM

Yeah I've had this happen to my Sanyo Z2. They replaced the whole optical block for me under warranty. And since then I've been extra careful to make sure I clean out the filter regularly. You won't be able to reverse what has already happened, but you can certainly slow it down by making sure you clead out you air filter regularly. Jus tpull it out nad eith vacuum it or blow it out with a can of compressed air. Hope this helps, Chris

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