[time-nuts] Are there any company selling refurbished/reconditioned Cesium tubes?

[Warren Kumari]

On Mon, Jul 1, 2019 at 6:35 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>
> Hi
>
> There are a lot of posts back in the archives about various things on Cs standards.
>
> Beam current is probably the best way to see “how much is left”. On a high performance
> tube, it drops pretty fast at end of life. That makes is a bit of an iffy measure there. If the unit has been
> in storage for a while, it may take a week to pump down to even get working ….. (and see the beam
> current).
>
> Most Cs standards you see for sale on eBay are listed as “parts only”. They may work, they may not work.
> The price is likely to be in the $1,000 to $3,000 range delivered. As soon as one gets listed as “working” the
> price goes through the roof ( like 5x to 10X). Since there is no test for “how much is left”, I’m not sure that is
> a good price to pay.
>
> So your choice is to pay a silly price on one that may last a couple months ( or may go on for years) or
> to pay a low price for who knows what. On the one with the silly price, you might be able to get some info.
> On the reasonable price units, the seller is probably not going to do much.
>
> From time to time, they show up here on the list. In that case the seller likely knows a bit more about
> the unit than the typical eBay listing. Even so, there are no guarantees. A unit that was working very
> well on the seller’s bench may run out of steam a few months later.

Speaking of....

I've been meaning to clear out my workshop for a long time, and am
finally starting to do so.
I have two "Datum PRS-50 Cesium Beam Primary Reference Source" - one
of them comes up and locks happily, the other logs an error which
decodes to " "ionizer supply - voltage (V) across the ionizer
filament" being too low (~0.5V when it should be ~1.6V). I *think* I
saw some mention of failing capacitors being a common cause of this -
I've been meaning to take readings from the good one, and comparing to
the bad to try hunt down the issue, but I haven't had the time.

I also have a FTS 4060 Cesium Time and Frequency Standard which works perfectly.

These are all just sitting in my workshop, and I'm feeling guilty that
they are not being loved -- and so I'm going to be selling them. They
are bulky / heavy (and I'm lazy!), and so I'm going to be optimizing
for someone who A: has a good use for them and B: can come pick them
up (I'm in Northern VA, near Washington Dulles (IAD) airport) instead
of maximizing the price... which I haven't even begun trying to figure
out yet..

A random, unsorted pile of pictures is here:
https://photos.kumari.net/Projects/AtomicClocks/

I'm currently traveling, but hope to get things better organized in
early August...
W

>
> Bob
>
> > On Jun 30, 2019, at 6:20 PM, Glen English VK1XX <glenlist at pacificmedia.com.au> wrote:
> >
> > Bob, are there any URLs you can point to, or provide advice on, if inspecting a Cesium for sale, is there an hour counter, or other metrics that can be measured in the tube department ? (I am familiar with TWTs, Klystrons etc so the HV doesnt bother me)  in order to ascertain the level of life left ?
> >
> > that is, apart from turning it on and waiting a while and measuring ADEV for a week.... on the sellers premises.
> >
> > glen
> >
> >
> > On 1/07/2019 7:09 AM, Bob kb8tq wrote:
> >> Hi
> >>
> >> Based on several replacements on a “high performance” 5071 …. 6 to 7 years of 24/7/365 seems to
> >> be about the point things start to get flakey. Maybe not dead, but crazy enough that it lets you know
> >> it needs a new tube ( = ADEV is not even close to what it should be ..).
> >>
> >> Cost several years back for the swap out was right at $40K. The process included hazmat shipping
> >> silly nonsense. That part delayed the process by almost 2 months.
> >>
> >> Bob
> >>
> >
> >
> >
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>
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-- 
I don't think the execution is relevant when it was obviously a bad
idea in the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair
of pants.
   ---maf