[time-nuts] Broken Ovenaire OSC 85-50 - crystal failure ?

[Kit Scally]

Bruce,

I'm 99% confident - I had the whole hockey-puk apart and manipulated the
capsule to get the unit working.  The assembly isn't under vacuum - it
just requires a bit of "knack" to prise it apart.  However, the crystal
puk is, I'm sure, under vacuum or filled with an inert gas (comments
please, Rick ?).  It's about 15mm diam.  I have some pix of the puk.
Can you email me privately how to upload pix to "somewhere" - I'll
download them tomorrow.

I'll wear safetly glasses ...

Kit

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bruce Griffiths
Sent: Saturday, 4 July 2009 6:38 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50 - crystal failure ?


Kit

If you are confident of your diagnosis then you have little to lose. The
crystal is defunct and isn't going to fix itself so it may be
instructive to take a peak inside. However don't the E1938 cans have an
internal vacuum? Some care in opening may be required.


Bruce

Kit Scally wrote:
> G'day Joe,
>
>
> My call on <this> question is: "very seldom with a properly designed 
> circuit and crystal" (NO flames please on these descriptions !) Having

> said that, I have a couple of broken crystals from once-working HP 
> E1938A oscillators.  All appear to have some form of physical fracture

> or electrical disconnect within the copper crystal capsule. A careful 
> shake makes a re-connection but fails if the capsule is moved even 
> slightly. I've not attempted to butcher a capsule open to determine 
> the cause - this to my mind is bordering on the sacrilegious but if 
> given absolution from another TimeNut, I may attempt it and photograph

> the results ...
>
> Regards,
>
>
> Kit
> VK2LL
>
> *************
> Do XTAL's fail often?  If so, by what mechanism?  Slowly fade away? 
> Sudden death?  I am not experienced enough to know this answer but in 
> all my years with various HAM gear, I do not recall the failure of a 
> single XTAL. However, none of these were in an oven.
>
> Thanks again for all the useful information.
>
> Joe
>
>
>
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