[time-nuts] Re: Oscilloquartz 8663-XS stability problem

[Attila Kinali]

On Sat, 28 Oct 2023 20:00:32 +0000
Brian K via time-nuts <time-nuts at lists.febo.com> wrote:

> "The phenomenon that you see may be due to moisture absorbed/adsorbed by one or more of the components. While in storage the unit equilibrates with maybe 60% RH. When the oven is operated the RH is reduced to near zero. (Each degree C reduces RH by about 10%)
> It may take weeks to settle."
> 
> The 8663-XS can is hermetically sealed so I doubt if it is a humidity problem.
> As I pointed out in the eevblog thread, there is a solder blob on the side of the can.
> I suspect this seals a hole used to fill the inside with an inert gas such as dry Nitrogen.

While most OCXO are hermetically sealed, it does not mean that an OCXO
bought from ebay still is. Years ago, I bought a bunch of "Trimble" OCXO,
which I suppose were relabled Vectron OC-050 or similar. I did measure
a handfull of those and most performed with decent long term stability.
But a few did not. They still kept drifting (up or down) at a rate way
beyond their spec after a month. With quite a few of them, I could see
that the glass insulator/passthrough of the pins were cracket. I.e. the
seal of the OCXO was broken. I suspect, that the OCXOs would have settled 
at some point, but that could have taken months or even years and I wasn't
quite keen on measuring that long. I thought about using a drop of epoxy
to seal the cracked passthrough pins and see whether that helped, but did
not get around doing that.

On Sun, 29 Oct 2023 11:46:56 -0400
Bob Camp via time-nuts <time-nuts at lists.febo.com> wrote:

> I think that the answer to the “double oven” question is that it is not one. The data sheets that have been tracked down do not make that claim. The tear downs do not show an inner oven. The device’s performance specs (and actual performance) are not in the double oven range. 

Bob, did you find tear downs of 8663s? If so, could you send us the link?
I have been looking for those for quite some time, but never saw any.
And my google foo does not seem strong enough to find them.

			Attila Kinali

-- 
In science if you know what you are doing you should not be doing it.
In engineering if you do not know what you are doing you should not be doing it.
        -- Richard W. Hamming, The Art of Doing Science and Engineering