NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Dolkas
Date: 2013 Dec 2, 21:11 -0800
Dan-
As for replacing the bulbs with LEDs there is a less drastic way do accomplish this – you can get LED bulbs that have a light bulb base, so there is no rewiring required. I did this to my A-12, and it works quite well. The lightbulb that lights the index scale really could use the extra light. As a bonus, you can get red LED bulbs in this shape format, so you don’t screw up your night vision. The only slight drawback is that red LED bulbs require 3 volts, so you will need to use a Lithium C-cell rather than an alkaline. Doesn’t cost a lot, and they will last forever.
As for the bulb that illuminates the bubble cell, this should be incandescent. LEDs can’t be dimmed by using a potentiometer, so unless you want to add a bunch of circuitry, just stick with a 1.5 V bulb. You can get them at RadioShack, if nowhere else.
Eric-
If you should come across an extra bubble cell for an A-12, or a potentiometer for the bubble lamp, please let me know. I’ve been looking for these parts for a few years now.
Thanks - Paul Dolkas
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Eric van der Veen
Sent: Monday, December 02, 2013 11:02 AM
To: paul@dolkas.net
Subject: [NavList] Re: Bubble sextant parts and calibration
Dan,
There’s a fair number of people here at NavList experienced with bubble sextants. If you are good with fixing things, as you say, and with some common tools, skills and a bit of help from people here you can definitely work on bubble sextants quite successfully. I started doing this only 2 years ago, and find it highly satisfying and rewarding.
A12’s are not very rare. A11’s are much less common, but spares for any are hardly ever sold separately. I expect to receive an envelope full of A-10 and A-12 spares parts within the next 2-3 weeks, and I’ll check for spare light bulbs.
A common technique for the bulbs is replace them by modern LED’s that will have to be placed & connected in the socket. Although that really is more renovation than restoration, there sometimes just isn’t a better option.
For some models (including tha A-12), an excellent restoration manual is available from Bill Morris, at
http://sextantbook.com/category/my-bubble-sextant-restoration-manuals/
Regards
Eric
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