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    Re: A-10 Sextant Maintenance Manual
    From: Jean-Philippe Planas
    Date: 2007 Dec 12, 11:25 -0800
    Hello Robert,

    You are perfectly right and I totally agree with you, A10s bubble assemblies are tricky. What I described is the process to refill the bubble to get it back in working order at least on a temporary basis to get the feel of it and take a few sights (by the way I really like the lighting system for night shots). Unfortunately It does not warrant final and durable success in any way.
    It is also my experience that all bubble assemblies gradually loose part or all of their xylene over time without any obvious leak or xylene characteristic smell.
    I have reconditionned 4 A10 or A10As and 5 bubble units and they all lost part of their xylene in a matter of months.
    Without refilling the assemblies in a low pressure container I don't think we can do any better.
    If anybody has a better experience on A10s, please speak up!
    JPP

    Robert Eno <enoid{at}northwestel.net> wrote:
    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 -----
    Sent: Tuesday, December 11, 2007 2:33 PM
    Subject: [NavList 4288] Re: A-10 Sextant Maintenance Manual

    As 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---.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, Camelot wrote:
    > 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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