[time-nuts] Symmetricom XPRO rubidium

[Bob kb8tq]

Hi

> On Sep 27, 2020, at 10:19 PM, Stewart Cobb <stewart.cobb at gmail.com> wrote:
> 
> I have a Symmetricom* XPRO rubidium which appears to be reaching its end of
> life. The very sparse manual says that it sets a "service" flag when the
> lamp voltage reaches 600 mV. When I got it, that parameter was at about
> 540. Several months of continuous runtime later, it's down to about 510.  I
> assume this is a measure of light emitted by the lamp, but its label is
> "lamp voltage".
> 
> I don't want to lose this Rb, because it seems to be the most stable
> reference in my lab (about 2x more stable with temperature than a PRS10, by
> eyeball).
> 
> Questions for the hive mind:
> 
> (1) Why and how is the lamp voltage falling?  What's the wear-out
> mechanism?

It’s looking at the photo detector on the physics package. The amount of
light getting to the photo detector is “getting low”. Once it gets low enough,
the SNR degrades. At some point that gets bad enough for the device to 
loose lock


> 
> (2) Is there any hope of repair? Will the heat gun trick for the LPRO work
> on the XPRO? Could I replace the XPRO lamp bulb with one from a young LPRO?

The devices are “aligned” to match up with the bulb. The various tweaks to get that
done are never documented on the Telecom Rb’s. You might get lucky, you might 
not.

If you have a working LPRO, there’s no real reason to expect the XPRO to work 
any better than the LPRO ( at least not after surgery ….). 

> 
> (3) Has anyone ever done surgery on an XPRO? Any hints or tips?
> 
> (4) Does anyone know anything more about the XPRO? I have data sheets
> 900-00542-000B and -000F, and manuals 098-00058-000 rev A and rev B. The
> manuals are just barely sufficient to get the thing running. The device
> itself displays parameters on its serial interface which appear to be
> adjustable but which are not described in the manual.

Sparse manuals are pretty much the way things are done these days. That’s not
just an issue on Rb’s …

Best approach is to start shopping …..


Bob


> 
> Thanks in advance for any help.
> 
> *Symmetricom has been acquired at least twice since this device was built.
> But the device label says Symmetricom, and the manual says Symmetricom, so
> I'll stick with that name for now.
> 
> Cheers!
> --Stu
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