[time-nuts] Re: Efratom FRK with "inoperative lamp"

[Peter Bell]

On Tue, Feb 1, 2022 at 6:25 PM Julien Goodwin <time-nuts at studio442.com.au>
wrote:

> "Terminal pin 7 provides an indication of proper operation of the
> rubidium lamp. For nominal operation the signal is 6 to 12V. An
> inoperative lamp is indicated by an signal of approximately 3V. The
> internal resistance of this circuit is approximately 6K."
>
> ... indeed I'm seeing 3v on that pin.
>
>
Start by checking if the lamp is actually striking - if not, check the 20V
supply on the lamp drive board and the
drive transistor (2N3553, IIRC) - also check that the lamp assembly is
heating up.  If the temperature seems
correct and the lamp is lit then another thing to try is inspecting the
lamp to see if the Rb has managed to migrate
to places where it obstructs the light coming out of the lamp - if so,
careful heating with a heat gun can rectify
this. You want all the Rb in the bottom of the lamp.

It's been years since I worked on these things, but they were generally
pretty easy to fix - the schematics are
available and uses all standard components.

Regards,

Pete