[time-nuts] HP Stories: An architectural view of the HP 5060/5061 and awkward oscillator adjustments.

[Bob kb8tq]

Hi

Well …. ummm …. errr …. it turns out that there *are* (or were) papers published on the topic that are
“well known” in the … errrr …. space community and pop right out of the stack of papers that the guys 
from …. errr ….  a well known space outfit in California bring with them ….

The issue is that below some magic percentage of the rated voltage, the dielectric may try to re-form.
When it does, the outcome is a bit unpredictable. As I recall it applies both to tantalum and aluminum 
parts. There are different factors for the two types.

Keep in mind this all came up in a meeting in the mid 1990’s ….memory is only just so good ...

Bob

> On Feb 25, 2019, at 9:56 AM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 2/25/19 5:48 AM, Bob kb8tq wrote:
>> Hi
>> Indeed there is both a minimum and a maximum working voltage for a properly derated electrolytic
>> capacitor. We found that out in the middle of a design review when the customer’s team brought it
>> up … (much to our surprise).
>> Bob
> 
> 
> The Cornell Dubilier app guide doesn't seem to mention it.
> http://www.cde.com/resources/catalogs/AEappGUIDE.pdf
> 
> NAVSEA derating guidelines make no mention of it:
> https://www.navsea.navy.mil/Portals/103/Documents/NSWC_Crane/SD-18/PDFs/Products/Capacitors/CapacitorsDeratingRevB.pdf
> 
> They're both appear to be focused on essentially setting a lower voltage as a thermal consideration, and not on a "giving you more margin to failure voltage".
> 
> https://www.illinoiscapacitor.com/pdf/Papers/reliability_of_capacitors_general.pdf
> 
> says you only get a max of twice rated life by derating.  Maybe that's because of the "reforming of the dielectric to a thinner layer"..
> 
> This is a compendium from 1981 of all sorts of capacitor information but doesn't seem to address derating.
> https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810017835.pdf
> 
> 
> https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003309.pdf has a lot of info on wet slug tantalums..
> 
> 
> 
> 
>>> On Feb 25, 2019, at 1:48 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
>>> 
>>> --------
>>> In message <CADHrwpcdmyeguXoM69D2byW=DfKwMfi7_t-P=qYst7T7OO=EuA at mail.gmail.com>, Dana Whitlow writes:
>>> 
>>>> This would seem to imply that purposely overrating a 'lyt is pretty pointless.
>>>> 
>>>> Any comments on this notion?
>>> 
>>> I've always wondered that myself, and found very little documentation or
>>> wisdom available.
>>> 
>>> As I understand it, even very brief voltage spikes must be kept under the
>>> rated voltage, so overrating would buy some transient durability, but
>>> other than that...
>>> 
>>> -- 
>>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>>> FreeBSD committer       | BSD since 4.3-tahoe
>>> Never attribute to malice what can adequately be explained by incompetence.
>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.