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

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@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 > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com >