[time-nuts] HP5065A C-field current is temperature sensitive

Chuck Harris cfharris at erols.com
Mon Aug 31 08:47:34 EDT 2015

Hi Bob,

I haven't seen anyone bashing the designer, or the design of the 5065.
What I have seen a couple of enthusiasts that love the unit enough that
they are willing to spend countless hours bringing a couple of parts of
the design up to a more recent state of the art.  Corby's modifications
to the optics added stability that no one anywhere has achieved in a Rb
standard.  PHK's changes to the oven may achieve a similar improvement.

Between the two of them, the 5065 is looking pretty nice!

In my experience, there are quite a few pieces of equipment where people
are willing to take the relatively minor effort to repair them to match
their original specifications, but very few where people are impressed
enough with the foundation parts that they are willing to spend the
great amounts of time it takes to fully understand and modernize the

I think that speaks well for the designers of the 5065.

-Chuck Harris

Bob Camp wrote:
> Hi
> As we go joyously bashing the poor guys that designed this beast, it’s worth noting
> just how old the design is. 741 op amps were indeed “modern” when they did much
> of this and quite possibly to modern to be trusted. Most of the design would have been
> right at home in the late 1960’s at a conservative design house. As time has shown, in
> a lot of cases that mistrust of the early linear stuff was well founded ….The 741 only
> was designed in 1968….The 5065 design dates to roughly that time.
> Bob

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