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    Re: A-12 Bubble sextant
    From: Ken Gebhart
    Date: 2006 May 31, 17:43 -0500
    Re: [NavList 348] A-12 Bubble sextant On 5/30/06 9:18 AM, "jean-philippe planas" <jeanphilippeplanas@yahoo.com> wrote:

    Hi all,  
    I just purchased an A-12 bubble sextant that seems in fine condition but features nevertheless a serious flaw.
    The Bubble Illumination Assembly (with a bulb on, and also named the Night Illumination Assembly in the manual) is stuck in the instrument thus preventing the removal of the bubble assembly in place (and also preventing any night shots as I cannot put a battery inside or change the bulb). I am also unable to clean this part of the instrument.
    Could anybody familiar with these instruments suggest a procedure to extract this Bubble Illumination Assembly because I don't want to do anything foolish that could damage the sextant or the assembly.
    May be Mr Ken Gebhart could provide useful advice to solve this probleme if he is still monitoring this list.
    Looking forward for any advice


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    The problem is that the light holder has a zinc part that holds the bulb inside.  They say that zinc expands with age, and accounts for it being stuck inside after many years.  Our procedure is to take the black rheostat cap off, and using a long screwdriver as a pry-bar, try to pry it out using a wooden block as a fulcrum.  Using Liquid Wrench or a penetrating oil may help.  If no luck, you must take the sextant completely apart in order to have access to the front end of the light assembly.  First, break the light bulb (if installed), then using a wooden dowel, try to knock the assembly out with a hammer.  This may well fracture the zinc casting, but at least you will have the unit out.  You could then jury-rig a penlight, or something to stick into the cavity in order to illuminate the bubble.

    Good luck,

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