[time-nuts] HP Cesium Standards in the International Atomic Time Scale, the legend of Felix Lazarus, and the "top cover

[Bob kb8tq]

Hi

Indeed back at Motorola, a lot of that stuff got transferred into the engineering stock room 
after a while. Just how that worked out budget wise …. one wonders ….

Bob

> On Dec 24, 2018, at 11:53 AM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 12/24/18 5:36 AM, Bob kb8tq wrote:
>> Hi
>> The gotcha is - if you have a very unique part in a device and it goes away, how
>> many years of stock do you buy on the “last chance” order?
>> In the case of the 5071, I’d bet a pretty good brand of six pack that nobody on the
>> planet would have guessed 20 years ago that it still would be in production today.
> 
> EOL buys for a product line are plausible.  But if you're building one-off (or limited quantity)- maybe not.  At work (JPL) there's a whole aspect to sparing that's kind of subtle - you get funded per mission, and it has a cost cap at the proposal stage.
> 
> Buying extra parts "just because" cuts into your budget - what do you give up because you bought extra parts, maybe some engineering hours? or test time?  - it's easy to say "oh what's a few parts here and there", but pretty soon, it's getting to be a big part of your budget.
> 
> So you buy enough parts to build what you're going to launch, plus enough maybe for an EM or breadboard, and then a few spares in case there's some assembly errors, or you need to scrap a board.  If the problem happens early enough, you've got time to burn some reserves and order more.
> 
> The other problem in the space business is that there is a lot of desire to re-use known good designs.  That part may have been a long way from EOL when it was first used, but now, 5-10 years later, maybe it's EOL, and there's no obvious "drop in" replacement.  Do you redesign, or do you buy the last remaining stock and hope for the best?
> 
> This tends to be a cascading issue - mission A designs and uses part X, and has spares.  Smaller Mission B uses the spares to build their widget using the Mission A design. They buy a few spares too. Smaller Mission C does the same thing.  Now we're 10 years in, in some cases still using spare parts bought by original Mission A.
> 
> I am still using spare connectors and such from Cassini (launched in 1997) in things like breadboards at work.
> 
> 
> 
>>> On Dec 24, 2018, at 1:59 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
>>> 
>>> 
>>> jimlux at earthlink.net said:
>>>> and the "market lifetime" of parts today is much shorter.  There are  lots of
>>>> parts from Hittite that were essentially "run on this line  only", and when
>>>> they moved geometries, they're never to be seen again.
>>> 
>>> Most vendors make a lot of noise before they pull the plug on a part.  The
>>> usual deal is that they fill all orders placed by a specified date - lifetime
>>> buy.  Distributors typically send a note to anybody who has purchased them, or
>>> maybe only purchased significant quantities.
>>> 
>>> If a part isn't expensive, you can afford to buy extras beyond what you expect
>>> to need to cover some what-ifs.  That probably doesn't cover something like
>>> the 5071 being in production for 30 years.  But it could give you a few years
>>> warning - maybe enough time to find a substitute and/or redesign that section.
>>> 
> 
> 
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