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

[Magnus Danielson]

Hi,

On 2019-02-25 07:48, Poul-Henning Kamp 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...
>
The trouble with aluminium electrolytics is that if not voltaged is 
applied, the oxide layer slowly breaks down. This is why the capacitors 
is stored charged and needs to have slowly increased voltage for the 
oxide layer to rebuild. If too high voltage is applied it breaks 
through. Now, over-rating could potentially not work very well if not 
operated at high enough voltage.

I don't recall for sure the reference for this, but I think some of it 
was out of AT&T Reliability manual. I'm too far away on travels from my 
library to check on details.

It's also a concern with boat-anchor equipment. Direct full-voltage 
power-up can make the caps blow in the PSU.

Cheers,
Magnus