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    Re: The development of bubble sextants
    From: Bill Morris
    Date: 2009 Aug 24, 22:34 -0700

    You wrote of your A12 sextant battery/bulb holder
    "I can pull the tube out about an inch or so, but no further. There are slits 
    in the walls of the tube and I can see light from the slit on the opposite 
    side. This means that I'm fortunate that there is no battery in the tube with 
    the resultant corrosion. Do any of you have any special tricks for removing 
    the tube? Heat/cold, etc.?" 
    The A12 is notorious for corrosion and the two battery holders should not be 
    stored in the instrument. You could try pushing it back in and removing the 
    bubble unit and popping out the tinted skylight. Then employ a small child to 
    apply some grease with its finger around the bulb holder, which is an 
    aluminium casting attached to the thin-walled battery holder. Also squidge 
    some grease through the slits from the inside while pulling and rotating. 
    Then try pulling harder while pushing with your own finger. Forcefully 
    rotating the thin casing with a wrench is likely to crush the rheostat 
    housing or buckle the casing.
    I once had to break up the bulb holder casting and remove it in bits - a bit 
    like old-fashioned obstetrics really - but the battery casing then came out 
    easily. It wasn't too difficult to make a new bulb holder.
    Bill Morris
    New Zealand
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