[time-nuts] Portable standard

[Greg Broburg]

 From what I have learned from people much
smarter than me, the one to buy is the PRS10
from Stanford Research. They were going for
under 200 a few years ago but are now up at
500 or more. From what I understand this item
is worth that money.

I own Efratom FRS-Ns which I paid 1000 each
for 15 years ago.

The bulbs do not burn out, there is no filament
in them. The bulbs are a glass container which
live inside of an RF excitation coil. If the unit
stops working it is generally not a failed bulb
On mine there was a resistor (10k) which
changed to 5k and stopped it. This resistor is
a known problem, same resistor failure in
many if not all units after a few thousand hours
of operation.

I have been party to repairing 10 FRK rubes.
In these units the tantalum bypass capacitors
are all suspect, some of them go shorted. We
replaced all of these caps and retuned them
and they are all up and running now.

I have been bidding for an EPS

Here is a quote from a few years ago from Corby
Dawson.

> Rubidium standard life
> Thu, 12 Nov 2009 10:13:22 -0800 Post Comments
> Glenn,
> The lamp is usually the limiting factor.
> The PRS10 advertises its lamp life to be 20 years.
> HP bulbs last a bit longer.
> Tracor bulbs fail with a different mechanism and last maybe 10 years.
> Efratom bulbs last at least 10 to 15 years.
> The rejuvenation you referred to is for lamps that have been off for
> years in uncontrolled temperature environments.
> These bulbs are not bad, the rubidium has just migrated to the wrong part
> of the bulb.
> With a little effort it can be coaxed back where it belongs.
> A really bad bulb can not be rejuvenated as the rubidium has been
> absorbed into the inner lining of the bulb envelop.
> Sometimes these bad bulbs show a definite envelope darkening to the eye.
> Hope this helps.
> Corby Dawson




On 4/6/2011 9:46 AM, Joseph Gray wrote:
> As usual, lots of good replies and more links to things for me to read :-)
>
> On the topic of rubidiums, I see three different brands on ebay. The
> FE units sell for much more. What are the differences between the
> three brands? Is the FE brand worth the price? Considering that these
> are all used units, how long before the rubidium lamp is  dead? What
> about powering these things? Any precautions?
>
> Joe Gray
> W5JG
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>