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  1. #1
    Really Senior Member Kev G's Avatar
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    IWS focusing help/advice

    The focusing on my IWS has never functioned and have started to have a go at fixing or at least finding out what the problem is by taking the front end off that houses the focus mech.
    A few questions if any one can help before I go further.
    Am I going to do and damage to anything internally by applying some releasing fluid to the threads that hold the locking ring C as it's very tight ?



    What do the 3 screws A do ?
    What does the screw B do ?





    Many thanks Kevin

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    Peter Laidler's Avatar
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    Screws A hold the focussing thumbscrew body to the main body. Screws B are red - and this should immediately tell you something. Yep......., red = desiccation screw into the OG housing. You won't damage anything per-se as it's all mechanical and optical operation in the OG system (as opposed to electronic). You will need to take extreme care to clean the lenses in a dust free and dry room.

    I say no more.............. except that I hope noone else in the universe is thinking of trying to adjust the focus using the OG lens housing

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    Really Senior Member Kev G's Avatar
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    Quote Originally Posted by Peter Laidlericon View Post
    I say no more.............. except that I hope noone else in the universe is thinking of trying to adjust the focus using the OG lens housing
    Thanks for the info Peter.
    As the Thumbscrew turns but there is no adjustment to focusing how do you get to the internal mechanical interface without removing the front lens ?
    I'm assuming something has stripped or broken.

    ATB KG

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    I don't have the EMER handy but in answer to the Q - thread 3, you remove that unit via the three(?) screws A and lift it out. There is a pin in there that rotates with the thumbscrew while engaging in a cam that moves an internal field lens back and forth to give fine focus for individual eyes (that is a real simplification) A bit like the 5 - 0 - 5 dioptre setting of your No2 binos. Another gross simplification I'm afraid.

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    Really Senior Member Kev G's Avatar
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    OK,I have undone the 3 screws and lifted off the thumb wheel with eccentric cam pin.The metal plate inside that the pin engages in just flops about and doesn't appear to act on anything ?



    Next removed the front lenses.



    The hole can be seen where the pin on the thumb wheel would be located but either a part is missing or something has broken not allowing something to slide/adjust ????

    Any idea whats missing or broken or how it should operate ?

    ATB KG

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    From memory, that plate, adjusting - photo 1, thread 5, - is attached to a field lens and moves it back and forth via the pin you mention and the thumbwheel. Basically, you can see that it should be connected to something......., but it's not! Clearly someone has 'assembled' it incorrectly and something is missing. I can't really help much further. As I don't have access to my parts list now - or can't find it, I can't really help from afar!

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    Really Senior Member Kev G's Avatar
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    OK Peter many thanks .
    ATB Kevin

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    Hi,
    here is a picture of how the part with the internal focus lens schould look like if you get it out. On the top sits the lens itself. You can see a little plate with the slit screwed onto its side. If you already removed the front lens, you can also simply pull out that shown tube. Either that plate is missing/loose OR the pin inside the thumbscrew itself is missing/broken/loose.

    Also little correction to Peter. The screw is not for adjusting eye errors/dioptrin, as that would be done in the eye piece lens. Because of the intensifier tubes viewscreen, the eye correction can only be applied for the focus from eye to viewscreen plate on the intensifier tube. The discussed thumpscrew is the adjustment for focus from close range to infinity of the target.



    :edit: I think the little plate is still where it should be, but the two screws that fix it to the focus lens assembly tube are missing. So in your case, the thumbscrew only moved the little plate, but the focus lens assembly stayed in its position.
    Last edited by Elphiel; 05-16-2017 at 09:49 PM.

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    To be fair, I did allude to your correction Elphiel in thread 2, line 3. But in order to keep it simple and correct the problem under discussion, I left it at that! Ocular focus is done with spacers below the ocular lens.

    There are TWO 'focussing' mediums. But let's keep it simple! What I fear is that in the future other owners will start on their IIW's using this as a pictorial guide.

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    Really Senior Member Kev G's Avatar
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    Thanks very much Elphiel.
    I can't move the internal focus tube that you have shown a picture of,does it slide inside the main body or inside another internal tube ?
    I will try and do a better picture of what mine looks inside.

    ATB Kevin

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