[time-nuts] Cesium tube ion pumps

Thu Dec 4 12:04:22 UTC 2008

That is my whole point,symmetricom will not come out and say it is defective
because it still is in within its operating parameters.

I checked with them on the warr before i bought this new old stock unit from a
surplus dealer.

at first they said I had no warranty because I did not buy it new but after
several calls they said they would go from the tube manuf date if I did not have
a receipt,

I then flew down to Florida to look at these units all still sealed in vac
pacs.new old stock from agilent,not symetricom.All sequential serial # manuf in
2005.I new all 8 of them were in storage 3 yrs and wanted to see the pump
currents in person upon power up for first time,The seller only wanted to unseal
two units to choose from so we set the two on a bench and plugged them in and I
immediately went to ion pump menu on both and was shocked they were both very
low upon initial power up.

I was surprised both started out below 5uA and both dropped to .2uA and .4ua
within seconds.even showing 0.2 after 5 minutes.

This must be due to them being brand new as I have seen several others,even a
gov liquidation unit that I flew to Texas to preview.This was a hp high
perf,manuf about 96 or 97.bad chassis.unknown tube.when I first powered it
up(this one has been in long term storage also) the ion pump overloaded and shut
down with a fatal error,so after 3 retries I got it to fall from 100uA down to
.2 and then 0.0 (but the unit was in standby due to the other problems)

this was a high perf tube from 1996 and the old style with only 5 years life (5
grams) the newer agilent tubes such as mine have more ceasum 8 grams instead of
five and say they last much longer..

I have looked at several other used 5071a also and all were after warm up and in
operate at about .2uA to .4uA..

One other change I have noticed in my tube since last year when it was brand
new.when I restart(power down overnight) the current starts out high up to 70-80
uA and falls in about two minutes to about 5.0 uA and then will dip down to
about 3.6 and back up to 5.0 even 5.6 yesterday.

when the tube was new it always stated out low 1.0 then dropped to .4 or .2,even
with the oven on, never over .4uA..

----------------------  Original Message:  ---------------------
From:    WB6BNQ <wb6bnq at cox.net>
To:      Discussion of precise time and frequency measurement <time-nuts at febo.com>
Subject: Re: [time-nuts] Cesium tube ion pumps
Date:    Thu, 4 Dec 2008 00:01:45 +0000

> David,
> 
> It would seem to me that while you have a warranty it would be prudent to 
> exercise
> such a warranty.  Otherwise, you will be fooling around till the last minute and 
> be
> out of luck.
> 
> If it sat "off" for three years and you have only had it operating for a short 
> while,
> unless I misunderstand something, it seems that there may have been a problem 
> with
> tube from the start ?  Out of curiousity, perhaps Corby can enlighten us on that
> aspect ?
> 
> Bill....WB6BNQ
> 
> 
> aceamusements at mchsi.com wrote:
> 
> > Corby,
> >
> > AT what point would be approp to call symmetricom and complain about defective
> > tube?I still have 2 years on the 5 yr warranty left, but how do u explain this
> > (defect),,(I assume it will just keep rising and eventually ruin the tube 
> within
> > a few yrs?)last I checked they wanted about 28k for a new tube.
> >
> > the unit with high perf tube has 5 yr warr from date of manuf. and cost 59k 
> new.
> >
> > ----------------------  Original Message:  ---------------------
> > From:    Corby Dawson <cdelect at juno.com>
> > To:      time-nuts at febo.com
> > Subject: [time-nuts] Cesium tube ion pumps
> > Date:    Wed, 3 Dec 2008 22:11:16 +0000
> >
> > > David,
> > >
> > > The long storage is not the cause. Extended operation of the ion pump
> > > causes the "whiskers" to grow. They can give rise to field emission
> > > leakage currents.
> > >
> > > This manifests as a raised ion pump current but does not inhibit proper
> > > operation unless the current gets too high.
> > >
> > > I don't remember at what current a 5071A will shut down at but I can take
> > > a look in the manual.
> > >
> > > Corby
> > > ____________________________________________________________
> > > Click here for free information on how to reduce your debt by filing for
> > > bankruptcy.
> > > 
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> > > VhPuk3kNAOgi96JqR/
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