Re: [time-nuts] Dead 5061B
Hi I want to inform you that my FE-5440a now works fine. After a lot of reverse engineering i found that there was a parasitic oscillation of about 500 Khz !!! in the integrator amplifier ic (lm108). I replace the ic with an other ( the same type but 7 years earlier production !) and now the accuracy is in the range of 1E-11. Now i have to play with c-field adjustment to achieve better precision. Regards Emmanouil Mantzaras -- Original Message -- Received: Mon, 04 Nov 2019 06:40:24 AM EET From: paul swed To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Dead 5061B Jim Is there any hope. I would believe so. CS tubes are pretty tough. As Scott says HV supplies but you measured those and they appear good as you say. So its a knock down drag out battle. You have nothing to loose so dig in. I wonder if the SRD may have popped. But its funny the ion pump is 0. That seems a bit odd. always a bit of crud in the tube that should make that kick up. My 10 cents. Regards Paul. On Sun, Nov 3, 2019 at 3:45 PM Scott McGrath wrote: > Have you checked the HV supplies? > > Content by Scott > Typos by Siri > > > On Nov 3, 2019, at 2:04 PM, AC0XU (Jim) > wrote: > > > > Time Nuts- > > This 5061B was working fine until a recent power failure, after which the > unit would not come on line (alarm light stayed lit). > > Major symptoms now: > > Beam I ; Second Harmonic; Ion Pump Supply are all 0 on front panel. All > other front panel readings are normal. (except for battery, which th unit > doe snot have). > > L4P2 signal is 16.832 MHz 1.7 V p-p (perfect - suggesting that A1 > synthesizer is fine) > > Going through 5-173 A12 Cesium Beam Tube Operational Checks: > > 5-175 Low Frequency Coil Check. Everything is fine except that tweaking > the external oscillator frequence/amplitude has no effect. Beam I is always > 0. > > The text says "If the beam current is not restored, it indicates a problem > in the the cesium beam tube power supplies (A11, A15, A18, or A19) or in > the cesium beam tube itself. > > A11 = Cesium Oven Controller - front panel reading is fine. Removed A11 > from the chassis and made the tests in 5-141. > Everything fine. +- 16V and -10V all fine; Cs oven voltage fine; the > thermistor tests out at 435 ohm vs. the 430 ohm on the label. > > A15 = Power Regulator Board - main +18.65V is fine > > A18 = +3.5KV supply - measured and is fine > > A19 = -2.5KV supply - measured and is fine > > I am inclined to conclude that the tube is dead. I don't understand why > that occurred suddenly in conjunction with a line power failure. > > Can I have any hope that the tube is still o.k.? Any ideas? > > Thanks! > > Jim > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] What to do with your dead cesium
Hello I wander if the guts from the dismantled cesium are available for a "transplant" in order to save a non working fe5440 with good tube. Thanks Emmanouil sv1bke -- Original Message -- Received: Tue, 21 Apr 2020 06:50:49 AM EEST From: Skip Withrow To: time-nuts@lists.febo.com Subject: [time-nuts] What to do with your dead cesium Hello Time-Nuts, Well, with the COVID-19 stay at home order I have been working on a couple of projects (at home). This post shows what I have done with an old FEI FE-5440A cesium standard. The tube was dead, so I decided to turn it into a GPSDO. I ripped out the tube, HV supplies, modulator, and OCXO. The battery was already missing, so it was replaced with a couple of SLA units. I decided to use a TruePosition GPSDO since it was small (I just wish it had a LOCK indicator). An SMA antenna connector was added to the rear panel. Basically, the 10MHz from the GPSDO feeds the distribution system in the FE-5440A. The TruePosition 1pps was brought out to the front panel, and can be used to synchronize the clock in the unit. An RS-232 DB-9 was put in place of the C-field control so Lady Heather can monitor. Some of the nice features are: 10MHz, 1Mhz, 100kHz, 1pps, and 1ppm front panel BNC outputs. Front panel clock display (that is easily set from the front panel) 1pps (FE-5440A) can be offset from 0-1 sec in 100ns steps from the TruePosition 1pps Battery backup (greater than 2 hours) and DC input, as well as AC input I don't know about the phase noise performance, but ADEV is probably better than the original standard (as long as there is a GPS antenna connected). I have attached a couple of pictures of the unit plus a 5-day TimeLab plot. Regards, Skip Withrow > - > Attachment: FE-5440A-1.jpg > MIME Type: image/jpeg > - > - > Attachment: FE-5440A-2.jpg > MIME Type: image/jpeg > - > - > Attachment: FE-5440A.jpg > MIME Type: image/jpeg > - ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[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 -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5440A cesium clock help
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" To: 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 -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
