[time-nuts] HP5061 Cesium ion pump question

Wed Dec 2 14:04:38 UTC 2020

Morris
I do see that of the 3 HP5061s the results are different and do know each
tube leaks or internally emits stuff. But as you say maybe the metering is
off. It definitely trips out at 40ua.
I have my units that pulse like that and then settle down as the tube
clears.
But its hard to explain that if a unit is pumped down how quickly it
pollutes again.
Wondering if as an example the getter just releases its captured crud when
the power is removed. That way you are always pumping down mostly the same
stuff.
Just very curious.
Regards
Paul
WB8TSL

On Wed, Dec 2, 2020 at 6:23 AM <vilgotch1 at gmail.com> wrote:

> I think there's quite a bit of variation in leakage rates between
> individual
> physics packages, and there's also variation in the accuracy of the
> metering. I recently started up my spare 5061A after over a year in
> storage.
> The Ion current meter showed zero with the Cs off but about 40 in the Open
> Loop position. I tried connecting an external +3500V supply through a
> microammeter as described in the manual and that showed less than 10 uA.
> The
> unit kept trying to start and pulsed for about 12 hours at a peak reading
> of
> 40 and then settled down nicely to a zero reading and hasn't missed  a beat
> since.
>
> I have a spare tube sitting here that hasn't been powered up for several
> years. It was removed from a junked 5061A that wouldn't start at all but
> after the unit was parted out some failed caps were found in one of the
> modules that could have explained the fault. I plan to try it on the bench
> with the +3500 V supply and microammeter but I don't know whether I can
> trust the reading. If the tube in one of my functioning units fails one day
> then I'll give it a try.
>
> Morris
>
> ------------------
> From: paul swed <paulswedb at gmail.com>
> To: Time-nuts <time-nuts at lists.febo.com>
> Subject: [time-nuts] HP5061 Cesium ion pump question
>
>
> During my HP 5061Cesium testing last week I was watching the ion pump
> current and am curious.
> What is the typical behavior people see on the tube after say 3 months of
> being turned off.
> With 3 units I see one that pumps doen from 8 to 2 in 40 minutes. Another
> maybe at 25 and takes 28 hours to get to 18. Just seems to be all over the
> place.
> Regards
> Paul
> WB8TSL
>
>
> ------------------------------
>
> Message: 10
> Date: Tue, 01 Dec 2020 06:19:25 +0000
> From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
> To: Discussion of precise time and frequency measurement
>         <time-nuts at lists.febo.com>, paul swed <paulswedb at gmail.com>
> Subject: Re: [time-nuts] HP5065a cfield issue
> Message-ID: <86443.1606803565 at critter.freebsd.dk>
> Content-Type: text/plain; charset="us-ascii"
>
> --------
> paul swed writes:
>
> > Guessing far less than 3 ma. by adding up resistors.
>
> More like typical 4 mA: there is a factory select resistor in
> parallel with the current-setting resistor.
>
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
>
>
> ------------------------------
>
> Message: 11
> Date: Tue, 1 Dec 2020 10:40:54 +0000 (UTC)
> From: ew <ewkehren at aol.com>
> To: time-nuts at lists.febo.com
> Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna
> Message-ID: <1292998389.3097482.1606819254766 at mail.yahoo.com>
> Content-Type: text/plain; charset="utf-8"
>
> Jim, I agree. As part of my OSA 8607A GPSDO project I planned to place the
> OCXO in an aluminium box to eliminate pressure change. Step one included
> buying a separate unit to make sure the rubber gasket did do the job.
> Attached first results. Temperature does change pressure more than ambient.
> The vertical steps are the result of gentle tightening the lid, did not
> know
> how much lid had to be tightened. Now I know and have a 10 day test
> running.
> With AC running, the AC control at the other end of the house lab
> temperature stays within ! C. Today a cold front hit, no AC and temperature
> will drop more than 1 C. Taking advantage of the forecast I am extending
> the
> test for a couple more days.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Doe to the low power
> dissipation of the 8607 fan cooling is not an option but I will use the box
> , seal it and characterize the 8607 for pressure and temperature and use
> external pressure and temperature sensors for compensation once combined
> with a new generation GPSDO.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??
>
>
>
> I'll bet pressure changes inside the "sealed" radome due to temperature
> changes are bigger than those due to local barometer changes.
>
> But an interesting thing - water vapor will go through cracks, porosity,
> that liquid water will not. The commercial success of GoreTex is an
> example of this, but cracks, o-rings that aren't quite right, etc. are
> also ways it can happen.
>
> Making a truly hermetic box is hard.
>
> >
> > -----Original Message-----
> > From: Poul-Henning Kamp <phk at phk.freebsd.dk>
> > Sent: Sunday, November 29, 2020 11:19 PM
> > To: Discussion of precise time and frequency measurement
> <time-nuts at lists.febo.com>; Art Sepin <art at synergy-gps.com>
> > Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna
> >
> > --------
> >
> >> It's obvious from the photo that the O-Ring seal failed its purpose
> >> over its many years of service. Has the unit totally failed or does the
> electronic portion still function?
> >
> > No, the electronics is stone dead.
> >
> > To me it looks more like water ingress through micro-cracks in the
> plastic-dome, and the O-ring did its job and kept that water in.
> >
> > The microcracks are uniform and seem to follow the molding flow, and that
> is probably to be expected in our climate:? We have a lot of humid
> freeze-thaw cycles.
> >
> > I wonder if buffing the radomes with car-wax would help ?
> >
> >> I said lucky because I found some GSynQ parts here in an engineering
> >> storage cabinet that we? can send to you at no charge to revive your
> unit.
> >
> > Thanks for the offer, but dont bother: I had a spare on hand, and I may
> still have third one lying around somewhere.
> >
>
>
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