NavList:

Here is the link to my earlier posting on making a 28 volt power supply.

http://fer3.com/arc/m2.aspx?i=106215&y=200809

gl

Gary LaPook wrote:

You're right, the electronic averger on the later models of the Kollsman periscopic sextants eat batteries,  A year or two ago I posted a way  to make a power supply that steps up 12 volt to 28 volts using one integrated circuit and one resistor, total cost about 25 bucks. You can search for it in the archive. If you don't mind being tied to an extension cord, an inexpensive way to get 28 volts AC is to buy a transformer for a lawn sprinkler which put out 28 volts AC.  The sextants work on either AC or DC.

gl

MikeN wrote:

I have a USAF type periscopic Kollsman D-1 sextant that requires 28
volts for the averager to work.  I tried wiring three 9-volt batteries
in series but the averager needed more power than the three batteries
provided.  I then copied the arrangement twice and then wired the
three series of three in parallel and it worked.  However, there's
significant power drain and the thing is only good for 2 or 3 shots.

Mike Nelson
Herndon, VA

On Jul 29, 6:58 pm, <douglas.de...@btopenworld.com> wrote:
  

Sorry not to reply until now. I have only just found you request. I only look infrequently here.

Mine is a MkI Hughes periscopic. I would expect them to all have the same connections with later Mark sextants.
There are three pins in a socket, the centre pin being common (Case, earth).  When looking at the pins from the back of the sextant (eyepiece away from you) the left pin is 3V for the bubble lighting, and the right pin is 28V DC for the averager motor. In fact it works from about 12V upwards.

I have a battery holder for two 1.5V cells which plugs straight into the socket enabling the sextant to be used for single shot sights, hand held, (heavy!) but without the averager. In fact I stand it on a suitable surface at the right height.

I have powered the averager from a separate power supply to check it and for the fun of it, but do not use it in anger for sights.

The power arrangements were designed for use with the aircraft fuselage mounting and power supply when connected of course.

Douglas Denny.
Chichester England.
    

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