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    Re: Lighting Problems w/ Aircraft Bubble Sextants
    From: Gary LaPook
    Date: 2015 Dec 29, 07:14 +0000
    And with the Kollsman sextants, both periscopic and hand held, you can replace the 28 volt bulbs with 6 or 12 v bulbs after you make up a small battery power supply. If you want to keep the 28 volt system then wire three nine volt batteries in series. If you have one with the electronic averager then you need to supply the averager with 28 volts but it eats batteries so better to use a 28 volt lawn sprinkler transformer or a solid state 28 volt supply powered off of your cigarette lighter socket (oops, politically incorrect, no one smokes anymore in California, must be a "12 volt socket") about 25 bucks in components. I have posted information about all of this in the past, just use the search box. 


    From: Robert Swartz <NoReply_Swartz@fer3.com>
    To: garylapook@pacbell.net
    Sent: Monday, December 28, 2015 10:39 PM
    Subject: [NavList] Lighting Problems w/ Aircraft Bubble Sextants

    All WWII U.S. bubble sextants that have an external battery case and cable plug w/ center pin work as follows:
    Bendix and B&L sextants: Center pin carries +3V potential. Outer ring carries -3V potential from 2 D cells. Instrument frame is  negative (chassis) ground.
    If you have voltage out of your battery case (verified w/ a meter) but no lights--oftentimes you have poor or no ground conductivity
    due to corrosion in the instrument or screws holding parts together. Clean corrosion and voila--lights (of course check bulbs and switch).
    A-10A sextants use a battery case w/4.5V potential from 3 D cells which drive the solenoid of the mechanical averager and have a resistor for 3V lighting.
    A-10 sextants use 2 D cell 3V lighting--Both are frame (chassis) grounded.
    The post WWII Kolllsman series of sextants use 28V aircraft power for lighting and are not supplied w/ battery cases. They are supplied w/power cables that plug and securely screw
    into recepticles on the sextant and aircraft.

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