[time-nuts] 5071A Cs Oven

[paul swed]

Brian
Funny you mention the dirty emult. At the time I was wondering and if there
was any insane way to get the Cs off the e multiplier. HV to ground or
something to migrate them.
Hold upside down and shake hard. ;-)
Regards
Paul

On Thu, Oct 4, 2012 at 4:22 PM, Brian, WA1ZMS <wa1zms at att.net> wrote:

> Rick can correct me on this...
> but my understanding is that it is
> almost never a case of running out
> of Cs from the oven, but that the
> dynodes of the electron multiplier
> become covered in used Cs and so
> the ultimate SNR and effective beam
> current falls to a point where there is
> no dependable beam current left to
> do much with.
>
> The tube that I sent to Paul, he was
> able to get some more current by
> running the Cs oven at a higher temp
> and as such is vaporizing off LOTS of
> Cs and can get a tiny bit of beam
> current to work with. But it is a down
> hill slide, since to keep the beam
> current up with a "dirty" E-mult, over
> time you need to keep running up the
> Cs oven temp to the point where you
> may just run out of Cs....or.... get an
> E-mult that is so covered with used
> Cs that there is no beam current to
> work with. You can always try and
> run up the E-mult voltage as well, but
> you then run the risk of arcing in the
> E-mult and an issue of burning up
> the resistor divider stack that I believe
> is part of the E-mult.
>
> I can see it now...... an end-of-life Cs
> tube that needs 35kV on the E-mult
> to get any beam current to work with!
> : -)
>
>
> -Brian, WA1ZMS
>
> On Oct 4, 2012, at 3:41 PM, paul swed <paulswedb at gmail.com> wrote:
>
> > Rick
> > Well I have the old 5060 and 61 tubes and indeed they run out O gas.
> > I am using a 5060 tube in a 5061 and the Frankenstein works though it has
> > only a few Cs. But heck it all locks after 48 hours.
> > So someone said with humor lets buy some 5071 tubes for a couple hundred
> > each.
> > Guess I could have some fun getting that into the 5061. Suspect that
> would
> > be the bride of Frankenstein then.
> > Thanks for sharing the insights and experience.
> > Paul
> > WB8TSL
> >
> > On Thu, Oct 4, 2012 at 3:21 PM, Richard (Rick) Karlquist <
> > richard at karlquist.com> wrote:
> >
> >> These ideas are "interesting".  AFAIK, there is very little
> >> chance of running out of Cs in many years, long past the
> >> time when something else in the tube will have reached its
> >> end of life.  Where did this idea come from?  Certainly, not
> >> anyone working at HP, Agilent or Symmetricom.  A LONG time
> >> ago, if you bought a high performance 5061, the increased
> >> Cs beam flow might have been an issue, but the amount of Cs
> >> shipped with the tube was increased before the 5071A
> >> such that running out of Cs is no longer an issue.
> >>
> >> If you turn off the Cs, you simply have a 10811 to connect
> >> to your GPS.  Except this 10811 has 10X the EFC range vs
> >> a stock 10811.  Again, this doesn't make a whole lot of sense,
> >> IMHO.
> >>
> >> BTW, another "interesting" idea is degaussing the CBT.  According
> >> to Len Cutler, this is completely unnecessary in the 5071A.  As
> >> anyone who knew Len can attest, if he thought something was
> >> good enough and didn't need to be improved, you could be
> >> sure about that.  For example, Len wanted us to use tantalum
> >> filter capacitors for energy storage in the power supply.
> >> Fortunately, we talked him out of that (actually the $100+
> >> cost helped to convince him).
> >>
> >> Due to customer demand (the customer is always right :-) the Santa
> >> Clara Division eventually released a degausser.  One of the reasons why
> >> this is not necessary in the 5071A is the Zeeman line measurement
> >> of the magnetic C field.  The 5061 was open loop.  So again there
> >> may have been a grain of truth behind the folklore.
> >>
> >> Rick Karlquist N6RK
> >> Member of the 5071A design team
> >>
> >>
> >> On 10/4/2012 9:45 AM, Tom Van Baak wrote:
> >>
> >>> Bob,
> >>>
> >>> Right, not good. There should be a fault message associated with it.
> >>> Check the internal log.
> >>>
> >>> OTOH, to conserve cesium, I've heard that some people run 5071A in
> >>> standby mode most of the time and only turn on the cesium for a
> fraction of
> >>> an hour a day or a week (to recal the quartz). Running in this standby
> mode
> >>> is also advisable if one wants the best short-term performance out of a
> >>> 5071A, without the loop noise. In this respect it's just like a GPSDO
> - you
> >>> get the best short-term performance if you turn off disciplining.
> >>>
> >>> /tvb
> >>>
> >>> Hi
> >>>>
> >>>> Is "Cs oven: 0.0V" a good thing on a 5071A?
> >>>>
> >>>> I suspect not, since either it or GPS is off frequency.
> >>>>
> >>>> Bob
> >>>>
> >>>
> >>>
> >>>
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