[time-nuts] Re: HP 5065A Rb, false "integrator limit" error

[paul swed]

Stu it looks like the integrator light is driven from A14. Its a simple
circuit with 2 zeners.
The control voltage into the board needs to be between 5.11 and 5.76. Or
somethings up with Q13 or Q17.
Good luck
Paul
WB8TSL

On Wed, Jun 26, 2024 at 3:06 PM Stewart Cobb via time-nuts <
time-nuts at lists.febo.com> wrote:

> I have a HP 5065A which has been running happily undisturbed for more than
> a year. Yesterday I noticed that the front panel "integrator limit" light
> is on. As far as I can tell, it shouldn't be on.
>
> On the meter, the "control" and "error" readings are both very close to
> zero. The signal on the back panel "control" jack is also very close to
> zero. Slight tweaking of the "osc fine adjust" control causes matching
> slight variations in the control signal, both on the meter and the jack, as
> one would expect. And the output frequency is stable like a good Rb lock.
>
> So I think the integrator itself is working fine, and the integrator limit
> error detector is broken. Has anyone seen this before? Any advice?
>
> Related question: the widely available service manual for the 5065A is
> dated 1979. My unit has a model date (first four digits of serial number)
> about five years later than that. Does anyone have the update pages for the
> manual, or a later dated manual?
>
> Cheers!
> --Stu
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