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

[Richard (Rick) Karlquist]

On 2/24/2019 4:02 AM, Rice, Hugh (IPH Writing Systems) wrote:
> Several people have asked about the Len Cutler ban on Aluminum Electrolytic Capacitors in HP Frequency Standards.   Rick Karlquist could shed more light on this too.   The legend of the ban was passed along to me, perhaps by Lou Mueller, who liked to tell stories of the old days.   In 1985, we were not taking the ban literally.   For example, the 2400uF main power supply filter capacitor was AL-Electrolytic, as were a few other smaller capacitors on the power regulator.   I sidestepped the capacitor issues on my simple battery charger by not having a filter cap after 
This discussion is the first I had heard of a ban on aluminum
electrolytics in the Cs standards.  All I know is that in
the early stages of the 5071 project, Len proposed using a
tantalum capacitor for the power supply filter.  None of
the members of the project time were aware of the history
of this, and we objected.  I vaguely remember the cap would
have cost something like $50.  Len eventually backed down on
that idea and in any event, the question became moot when
we went with the Vicor power modules, which surely had
aluminum caps at the front end for energy storage.  The
Vicor's seemed very avante garde at the time, but in practice
they worked very well and were very reliable.

A related thing happened in other instruments.  Previously,
power supplies in instruments were built from scratch,
and there were various reliability dictates, like derating
capacitors, etc.  Then it started to make sense to purchase
off line switchers.  These violated all sorts of "rules",
yet they got a pass and became SOP.  The R&D lab manager
at Santa Clara Division famously said "no customer chooses
HP products because they have great power supplies."

Rick