[time-nuts] insulation/packing material for OXO?

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Dec 16 18:53:24 EST 2006


Christopher Hoover wrote:
> Folks -
>
>  
>
> I've got several OXO's suffering from disintegrating insulation between the
> can and core.   The insulation in these OXO's is the greenish grayish foamy
> stuff.  It turns to dust over time.
>
>  
>
> The two units I opened most recently also had mechanical damage (broken
> crystal, broken solder connection).  I hypothesize this is a result of the
> disintegrating foam allowing the core to bang around inside the can.   The
> OAC 10MHz OXO from my 3856C actually rattled.
>
>  
>
> I've since fixed the broken solder connection and gotten the oven and
> oscillator to work.  Now I need to repack the core into its can.
>
>  
>
> What kind of material is this greenish-grayish foam?   Is it easy to get?
> Easy to work with?
>
>  
>
> If not, is there another material that works well and is easy to source?
> It seems like HP used a Styrofoam of sorts on the 10811.
>
>  
>
> -ch
>
>  
>
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>
>   
I should have mentioned that you don't want to increase the thermal 
resistance from the oven to ambient to a value much greater than the 
design value or the oscillator dissipation will by itself overheat the 
circuitry within the oven. The oven controller will lose control at a 
lower ambient temperature than intended
if the thermal resistance from oven to ambient is increased over the 
design value.


Bruce



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