NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: A-10 Sextant Maintenance Manual
From: Robert Eno
Date: 2007 Dec 11, 19:37 -0500
From: Robert Eno
Date: 2007 Dec 11, 19:37 -0500
A few comments from the backbenches.
I have a bit of experience in fixing these units
and can tell you that they are difficult. Did some repairs to my own A10 -- a
refill -- but it only lasted a few months. Having had some success with my
own (albeit short-lived) I felt rather cocky and so agreed to try to fix an
unit for a fellow in the States. I am still struggling with them after a
year.
In short, the A-10 bubble unit is a supreme pain in
the arse. I only keep my A-10 for collection purposes. Other than that, it is
virtually NFG due to the faulty bubble unit. Nothing at all like the RAE MK IX
and the Plath which, though finicky at times are, nonetheless
repairable.
If you manage to get it to work, perhaps you can
throw a few pointers my way. In the meantime I will continue to cope with my
A-10-induced low self-esteem.
cheers
Robert
----- Original Message -----From: jean-philippe planasTo: NavList@fer3.comSent: Tuesday, December 11, 2007 2:33 PMSubject: [NavList 4288] Re: A-10 Sextant Maintenance ManualAs I am not sure this answer went through the net and reached Arthur, I repost it.
If it did go through the net, please disregard it.
The bubble assembly has to be refilled with xylene which is some kind of a paint solvent.
You have to separate the bubble assembly from the main sextant body.
1- Unscrew the 2 small screws that maintain the lighting arrangement below the assembly.
2-Unscrew the 4 main long screws to separate the bubble assembly from the optical system.
3-Unscrew the bottom lens of the bubble assembly
3-1 with a wristwatch caseback wrench, unscrew the lens retainer ring.
3-2 carefully remove with a blade the metal and paper compression gaskets
3-3 unstick the lens with a thin blade or a suction cup
4 Remove the thin lead inner gasket and be prepared to replace it by neoprene O ring that fits in the lead gasket channel. The O ring is about 1.5mm thick by 20mm diameter.
5 Take out all remaining fluid by operating the enlarger knob back and forth
6 Clean the lens and inner of the bubble assembly with fresh xylene and Q-tips
made of natural cotton
7 Pour fresh xylene into the cavity (top it up) and work the enlarger knob back and forth to eliminate air from the reservoir. Repeat the operation until no more bubbles appear from the reservoir.
8 Top up again the cavity with xylene
9 Place neoprene O ring in place and lens
10 Replace paper and metal compression gaskets above the lens
11 Replace the bottom lens retainer ring and screw it by hand only
12 With your fingers of one hand applying controlled pressure on the top and bottom lenses, with the other hand carefully work the enlarge-reduce knob until a small bubble appear
13 Tighten the bottom retainer ring with the watch caseback wrench
Check the bubble after one or two days. If it grows you will have to repeat the process. Sometimes it is necessary to repeat the process numerous times until you get a stable bubble of the right size (about 1.5 or 2mm diameter)
The enarge reduce pump system will most likely not be working anymore as these bubble assemblies used to be filled under a vacum to correctly operate as specified.
Hope this helps
JPP
glapook@pacbell.net wrote:
Gary writes:
I will look at my A-10 manual tonight to see if it has this
information.
gl
On Dec 6, 11:56 am, Camelotwrote:
> I need assistance in loading or refilling the bubble on an A-10 WW II
> Air Force Sextant. If you can help, or direct me to help, please
> replThank you.
>
> Arthur Hill
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