[time-nuts] Re: HP 5061Bs on ebay

[Bob Camp]

Hi

Yet another layer to this will always be “what’s the objective?”.

If the goal is simply to have a Cs and play with it, then indeed the 5061 is a good 
target. Going after a 5071 is a step up in cost. There is no problem with this being
the objective. 

If the goal is some level of accuracy / stability / ADEV then this gets more way 
more complex. Some form of disciplined Rb quickly makes its way onto the list
of things you look at. Even with a GPS (and it’s cost) attached, the Rb likely will 
be competitive both in terms of cost and performance. Rb’s wear out, but the 
typical used item likely lasts longer than a used Cs. 

Lots of choices. 

Bob

> On Jun 15, 2023, at 8:55 AM, paul swed <paulswedb at gmail.com> wrote:
> 
> Totally agree with the comments its a real gamble. Even if it says the tube works what does that mean? The beams high enough to lock. I can tell you the beam can be unreadable and the system will lock. I have a 5061 unit with 0 beam and the metering circuit is not bad.
> That gets to Bobs comments well its locked but how good. The noise is higher and the stability is noisey. It can be seen using a good reference and a scope. But on average it tends to stay put.
> The unfortunate reality is the asking price is something but at 60 LBs the shipping is expensive.
> By all means go for it. It has been a great education for me at least working with the 5061s and FTS.
> But go in eyes wide open.
> Good luck to you.
> Paul
> WB8TSL
> 
> On Thu, Jun 15, 2023 at 1:44 AM Bob Camp via time-nuts <time-nuts at lists.febo.com <mailto:time-nuts at lists.febo.com>> wrote:
>> Hi
>> 
>> There are a *lot* of 5061 chassis running around. There are *very* few working 
>> tubes to go with those chassis.  The tubes wear out, but the chassis gets kept
>> “just in case”. 
>> 
>> It is not unusual to buy a half dozen or more in order to find one with a tube that 
>> “kinda sorta” works. Many of the ones that do get running are not very close to 
>> their original spec performance. (The stability of the unit degrades as the tube 
>> wears out …..)
>> 
>> For a while FEI had a contract to supply replacement tubes to the US government. 
>> You will find those tubes in some units. You also will find units with tubes out of other
>> brands of Cs standards. How well those work is a bit of a “that depends” sort of thing. 
>> 
>> None of this is to say “don’t do this”. It only is a caution that the route from having
>> nothing to having a good performance unit may be pretty long. You might get lucky
>> early on …..
>> 
>> Bob
>> 
>> > On Jun 14, 2023, at 6:09 PM, Ke-Fong Lin via time-nuts <time-nuts at lists.febo.com <mailto:time-nuts at lists.febo.com>> wrote:
>> > 
>> > Hi everyone,
>> > 
>> > So unfortunately, no, I won't be able to buy the newly introduced
>> > 5071B (or rather revamped 5071A) :)
>> > 
>> > However, and you probably know already, there's a few 5061Bs from one
>> > particular seller.
>> > They're pretty tempting, and I'm considering making an offer.
>> > 
>> > They seem to be later models (late 80s), and some of them even have
>> > "tube good" or "tube ok" sticker on them.
>> > Some are missing bits and pieces (like HV supplies) but with the
>> > cesium tube. And it seems that parts other than the cesium tube, are
>> > easy to find (lots of 5061 with dead tubes to scavange from).
>> > A few seem even customized, perhaps by Frequency Electronics? For
>> > internal use? Seems that they've added some monitoring circuitry.
>> > 
>> > Any comment, especially on the tubes, their remaining life or lack thereof?
>> > Still a project, but that's really something I start considering.
>> > 
>> > Best regards,
>> > 
>> > -- 
>> > /* Lin Ke-Fong
>> > * anotherlin at gmail.com <mailto:anotherlin at gmail.com>
>> > * I always do what I say, especially if it's something stupid.
>> > */
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