Burnt polarizor in an LCD video projector

Well errupted if not burnt. The other 2 polarizors and LCD panels look fine. This one is opposite a frame for its LCD , made of aluminium, that seems to have corroded , or at least loads of white powder on and around it.

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over some squared paper. Could an excessive amount of dust on the polarizor surface have caused a local hot spot, or some chemical process going on. Robbing a polarizor from a 7 segment display and crossing with one of the other projector polarizors gives a plum colour, wheras 2 of the original are brown. I suppose better than the disrupted spidery discoloured image before, a different colour cast in the "blacks"

Reply to
N_Cook
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Since maybe the late 1990s, a lot of video equipment (including the projector itself?) seems to default to a blue screen if there is no input / media present. Maybe somebody left it running in the "blue screen" condition for an excessive amount of time?

Matt Roberds

Reply to
mroberds

projector itself?) seems to default to a blue screen if there is no input / media present. Maybe somebody left it running in the "blue screen" condition for an excessive amount of time? "

This is not CRT technology.

The light is produced at maximum all the time by the lamp. The picture is p roduced by blocking it. As such, NOT blue would tax the system more than bl ue. If the screen is black, most of them waste more power, make more heat f or the simple reason that the light is not allowed to pass.

I remember in the CRT days we got some bad blue tubes in RPTVs. In some bra nds I figured out it was because they wenyt to an RMS type of detector for beam current limiting. Since the blue was always driven harder, and collect ive detection of beam current would allow more blue beam current.

Alot of VCRs did that blue screen thing, not always the TV. People would fa ll asleep and their video tape movie would end. Made me money actually. The most frequently changed tube in those things was the blue. I did hundreds of them.

Reply to
jurb6006

I need to elaborate a bit.

This is the polarix=zing filter. It is not something that MORE blue light passes through when blue is on the screen. It's function is to BLOCK the blue light that is anti-polarized from its axis when blue on the screen is not desired.

Reply to
jurb6006

I thought the blue tubes just had to be driven way harder to get the required brightness. Do you know if this is true, at least in RPTVs?

Reply to
Cydrome Leader

required brightness. Do you know if this is true, at least in RPTVs?"

I THINK, on a molecular level that because the blue has a shorter wavelength, it posed the same problems as it did when LED technology came up. You are sending BLUE light through there, not RED or GREEN which are longer wavelengths.

It is hard to explain sghort. It has to do with the fact that higher frequency wavelengths have an inherent higher energy.

This is beyond the scope of this group and its intent.

I think.

Is it really ? Electronics is a part of science.

But...

Reply to
jurb6006

Another point to consider is there is no sign of the LCD problem on any of the 3, often seen with DVM say, when left in bright sunshine, and black bleeding across the screen. Is the construction of these tiny projector LCD arrays a different construction and the crystal cannot bleed out of well if overheated?

Reply to
N_Cook

Back to a good blue background (for how long as just ordinary low temp LCD display polaising film transferred) , not tried a video feed. Going through menu info , the white text is clear but there are displaced minor ghost colour images of the text, like the CRT type of projector with out of adjustment colour feeds. How come there is good white but also displaced images.

Reply to
N_Cook

Someone had been in here before. Each of the 3 LCD holders is held to a steel frame with countersunk head , perhaps 1.5mm machine screws , in countersunk holes of the subframe. 3 corners only, the fourth not having a tapped thread in the mount. But one of these 3 screws was missing and one of the 3 on another LCD was loose. I assume a tinkerer had played with them. Countersink arrangements , however precise , I cannot see being precise enough for sub-pixel alignment of a 1cm or so diagonal LCD. The combined LCD holder and its subframe is held to another frame combining all 3 . Each subframe has 4 pins and located in 4 holes of the overall frame and the holes filled with epoxy or something like that. Would that be where the precision alignment on a factory jig would occur? The only way I can see of getting anywhere near any re-alignment is :- There is a little space to fiddle with the red and blue frames through available aperatures and align them to the green one which is unaccessible, so keep that one fixed where it is. With the provided countersunk screws and pits, that will not work. Perhaps temporary longer cheesehead screws and springs under each would give enough suck it and see and then stay in place manoeverability . Perhaps a dab of epoxy on each of the 2 corner screws would be enough to keep in registration , while removing the optical block , without the flimsey ZIF ribbons dislodging the frames, then fix more permanenly.

Reply to
N_Cook

Found a replacemnent countersunk screw but misaligned image Blue displaced 8 pixels rigth and 1 down Red 10 right and 8 up. May as well have a go with sprung small screw temporary replacements, can't make the situation worse. At least the misalignment seems to be vertically and horizontally consistent, just displaced parallel.

Reply to
N_Cook

much much reassembly is required between each adjustment and testing the alignment of the LCDs and other junk in optical path?

this project sounds pretty long.

Reply to
Cydrome Leader

I like a challenge, it was thrown out anyway. What is the saying ? "The difficult is done at once; the impossible takes a little longer"

Reply to
N_Cook

Ha.

I offered to fix a camera recently that served no other purpose other than to learn or something I didn't pay for.

Reply to
Cydrome Leader

Even better if you make a repair brief for the interweb thing, even if just how to get inside things

Reply to
N_Cook

I've been thinking about this for a while in fact. The problem is making a video is almost more work than any repair, and working solo makes it even harder. If I can come up with more space for a new workbench there may be a chance of this.

Reply to
Cydrome Leader

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