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    Re: Kollsman periscopic sextant mount
    From: Paul Brewer
    Date: 2015 Jan 04, 08:57 +0000

    Hi Dave,
    The International colour code puts red as 2 so I doubt that is what its about. Possibly, and here I
    speculate, there were some different voltage bulbs used in the vacinity of the sextant. I had
    hundreds of the things at 24Volts for the dash board of an Argosy. I remember a cardboard box with
    at least 2 pounds weight of the 24V lamps. As I don't remember any sextant on the Argosy there were
    much fewer of the 3V version, those had arrived from stores occasionally by mistake. The 3V versions
    were kept in a sealed box marked �V do not use!
    LEDs are current devices so what you need to do is have sufficient voltage then use a resistor in
    series to reduce the current to the correct value. I have hundreds of ultra brights here that I
    don't use because they are too high a forward voltage for my 3V supply constraint.Mostly they are
    around 4V with varying currents depending on type. Tell me what voltage you want to use and I can
    sort you out an assortment with any required resistors. I would recomend something like 3 AAA or AA
    cells in a holder. That gives you 4.5V and enough life for a seasons use. 
    I have a couple of Kollsmans one German the other ex Nimrod. I can't get at them at the moment
    otherwise I would do some experiments myself.
    I appear to have lost your email address I am at g4osj uk, I suggest we take this up off list so as
    not to bore the others.
    On 3 Jan 2015 14:16:31 -0800, you wrote:
    >Hello Paul.  Long time no hear from you.  Yes it's a black back red spot.  
    That's what makes it so strange, it's a Hughes'/Smith's bulb.  Any idea how 
    the red spots got on them?  There must have been a very bored airman one day. 
     It's not the old resistor spot code is it?  I find it hard to believe that I 
    might have crept down one night and slipped it in there.  I don't ever recal 
    having the Kollsmans, the Hughes, and the Smiths out at the same time.  Still 
    anythings possible these days!  I almost bought two more 9V batteries this 
    afternoon to try the Kollsman on 27V, but I had a last minute fit of meaness 
    at the check out, so I'll have to wait until my next Amazon order.  I'm only 
    looking for 80mA max, and I don't really need the counters light, so that 
    would mean 40mA max.  On the led front, do you know the best voltage for 
    cheap ultra bright leds, and do you need a resistor in series like the old 
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