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masking off unused tube

Discussion in 'Projectors, Screens & Video Processors' started by squid, Sep 16, 2001.

  1. squid

    squid
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    hi guys <br />i have been seeing a lot of talking about filling the gaps between the lenses and the face of the tube within a crt projector.

    i would like to do somthing like this . seem a good idear to stop reflections and light from filtering over from the other tubes

    can anyone give recomendations on how to go about doing somthing like this? what is the best thing to us ect?

    i was allso thinking about the light produced outside of the image by the tubes. i remember gordon saying somthing about masking the front of the tubes so this light dos not effect the pic

    i don't think anything has realy been mentioned about how to go about doing this . i am guessing that just sticking some black tape on the unused tube face is not the best thing to do, so how do you go about it?

    any help on these two subjects. i have painted just about everything in my cinema black . but what is the point if there is so much unwanted light being produced by the pj it's self. without doing somthing about these two isues i would have thought the best pic pos will never be produced

    any idears welcome<br />simon
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Simon,

    I've done this. Here's the method I tried to use. I tested it on StereoStereo's dem Sony1251q projector. The idea is the same for all air coupled crt projectors. You can't do it with liquid COUPLED (not cooled) units and you wouldn't need to anyway.

    You'll need:

    1 screw driver or nut runner, to remove lens assembly<br />3 pieces of tracing paper<br />1 large section of BLACK picture backing card form an art shop<br />1 section of either black felt or black velvet<br />Some glue or sticky tape depending on how permanent you want this to be.<br />1 craft/stanley knife

    NO OLD fairy liquid bottles required!

    Ideally you are trying to stop any light energy from the unused part of the raster from exiting the lens and at the same time stoping internal light reflections in the lens barrel washing out the original picture's light. Hope this makes sense.

    I made sure I had done a final set up of geometry and position before doing this as masking the tube face is something that will be unique for every different installation.

    So, once you are sure it's all in the right place remove the lens assemblies, being careful to not mix them up and to not scratch them..... I also took the time here to clean them with a photographers lens cloth.

    Now clean the face of each CRT as usually they are manky with s/h units.

    Next feed a signal to the projector. Make sure it's the larges aspect ratio picture you'll be showing on the thing. ie 1.78:1 for 16:9 screen or 4:3 for 4:3 screen.

    Get the tracing paper and mark out a template of the face of the crt and the position of the illuminated image on the face of it. Do this for each colour.

    Now, get your black card and using the template mark out on the card the shape to cut. IE You want a square looking(probably) shape with a rectangular hole in it where the image will shine through. With the image shining on the raster line them up and tape them or secure them somehow on the face of the tubes. Remember that you want to make sure the lenses will fit straight back on. If you have done it OK and there's no blanking of the image then remove the card and go get the felt or velvet. Cut out an identical template for each mask and glue the felt on to it so that when the mask is re-fitted again the felt or velvet is facing the screen (not the tube face). This will soak up light being reflected back towards the tube face. Now re-fit the mask again and check the lenses still fit easily.

    OK. The next bit I didn't do as it wasn't my projector but I would with my own. You want to try and find a way to line the internal barrel of the lens assembly with black velvet or felt between the tube face and the first rear of the first lens. I'd rub or shake the felt or velvet vigorously first to remove any fluff in case it falls on the lens inside.

    Once all this is done re-assemble. Re-do focus and convergence touch up and then re-do brightness and contrast as at least one will have changed (brightness).

    So, hope this helps. I did the first bit and we all thought it was a VERY worthwhile thing.

    ANYONE DOING THIS DOES SO AT THEIR OWN RISK. IF YOUR PROJECTOR BLOWS UP OR GOES ON FIRE THEN IT'S NOT MY FAULT OK!!!!!

    <br />Have fun guys
     
  3. squid

    squid
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    thanks gordon .

    i may verywell carry this out . i have to wait a little while though . the screen is not permenently fixed as yet .i have things to do to the screen wall and would'nt want to do it and find my screen has moved a touch and the image will no longer fit

    thanks for taking the time .verry informative <img src="smile.gif" border="0">
     
  4. squid

    squid
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    just thought i would add

    just for now (i finnaly got a long screwdriver) i removerd the lenses and gave the back of the lense and tube face a good clean with a lense cloth .

    i highly recomend that anyone buying a second user unit do this befor anything else . just doing this the improvment in focus and brightness is amazing <img src="biggrin.gif" border="0">
     
  5. squid

    squid
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    LOL good one Roland

    it's my electrohome ecp 4500
     
  6. Roland @ B4

    Roland @ B4
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    Squid<br />Which PJ are you doing this to?

    PS LCD people could try the same test but not cut the hole out.
     

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