[time-nuts] Symmetricom XPRO rubidium

[Stewart Cobb]

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?

(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?

(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.

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