[time-nuts] FE-5440A cesium clock help

[EMMANOUIL MANTZARAS]

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" <sv1bke at usa.net>
To: <time-nuts at lists.febo.com>
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


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