I think that the problem is at the modulation or discrimination circuit. When the loop is open, at the mass spectrometer amplifier, i have the modulation frequency (83Hz) and his second harmonic. The 83Hz component level is about 25db over the noise level when system is de-tuned and disappears in the noise when the oscillator meets the Cs hyper-fine frequency. The second harmonic level is about 15db over the noise. When i close the loop, the 83Hz increase slowly and stabilized at the same level as the second harmonic. This is a very strange behavior. Something happens in the discriminator circuit. C-field voltage is in accordance with the tubes label (5.05 volts). Hot wire voltage is 6 volts (5.5v in the label) and mass spectrometer PM voltage is 1807 volts (1550 written in the label). When i set the PM voltage in the correct value and there is a decrease in 83Hz s/n. After that i believe that the tube health is good. Any suggestions? Thanks Emmanouil Mantzaras
------ Original Message ------ Received: Thu, 31 Oct 2019 02:04:17 PM EET From: "EMMANOUIL MANTZARAS" <[email protected]> To: <[email protected]> Subject: [time-nuts] FE-5440A cesium clock help Hallo group I recently acquired an FE-54440A cesium beam clock. I do not know nothing about his history. Seems to be connected to the mains by the previous owner (a surplus broker). The meter readings seems correct. Supply voltages are ok, Vac-Ion current reading is about 0 (strange because that i believe that the unit was in storage for a long time). After about 20 minutes the cs and osc ovens stabilized. With loop open the beam current peaks at the correct oscillator frequency. The unit turns in "operate" condition when the loop is closed. The second harmonic level is ok with little fluctuation. With unit in "operate" condition and after 12 hours of warming, there is a constant frequency difference of about 0.003 hz from my two Z3801 gpsdos. Any idea about this condition? Any help is appreciated. Regards Emmanouil Mantzaras sv1bke _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
