NavList:

K McGraph you wrote: Does anyone know what voltage the black and white connector requires and what the connections are. The bulbs appear to be 3v. Can't see the colours of the wires inside the connector as they are rubber encapsulated.

 I got a Mk2A sextant out this morning.  The centre pin is -Ve, and the sextant is body earthed through that pin also.  You can confirm this by placing an ohmmeter between the centre pin and any bare metal on the body.  The right-hand pin as you look directly at the socket is for +3V, so RIGHT is RIGHT.  You can confirm this by placing an ohmmeter between the centre and right-hand pins and pressing the button on the handle or by winding the sextant up and adjusting the dimmer control.  The resistance will change.  The left-hand pin is for +28V for the heaters.  You shouldn’t need to use the heaters if you’re only operating on the at sea level. Following shortly will be photos of the relevant section of the Techies AP and of the 2xAA battery power supply I use.  DaveP