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    Lighting Problems w/ Aircraft Bubble Sextants
    From: Robert Swartz
    Date: 2015 Dec 28, 22:09 -0800

    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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