[time-nuts] R&S XSRM Rubidium

paul swed paulswedb at gmail.com
Sat Jan 22 22:31:41 UTC 2011

Well pretty interesting late afternoon.
The oscillator works but C-11 definitely is troubled. Additionally a key
element is an effective ground. Bridge the low side of the ampule to a
better ground and the oscillator seems to reliably start. Ignition occurs
when the oscillator is in the 80-85 MC range. It can tune from 65 to 130 MC.

Now the neat part.
That 1-2 mm silver dot that I see in the ampule. When warm it actually moves
around as you tilt the lamp assembly! Like  drop of water would but very
slowly. So I think this is the RB Magnus speaks of. I will need to peel the
mica cover off the area to try to heat this up and return it hopefully to
The fact that the dot moves means I may be able to get it to the center of
the sphere to more easily heat it.
Magnus when you heated yours did it simply vaporize??? Or did you get it to
simply move down deeper in the core area?

Other thing, measuring ignition time. On the first run just for the heck of
it I flashed a led light into the ampule and it ignited instantly. So
perhaps for old hard starting end of life RB lamps this might be a trick to
at least get it going for a bit longer.

Letting the RB lamp cool to room temp for another run.


On Sat, Jan 22, 2011 at 1:22 PM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> On 01/22/2011 07:03 PM, paul swed wrote:
>> Interesting
>> Took the oscillator board apart last night and found C11 has a cold solder
>> joint.
> That explains it.
>  Its the variable cap that tunes the heater. Have not re-soldered it
>> yet as I am having trouble getting enough heat in the area even with a
>> soldering gun to tack the cap back on to the housing.
>> Fortunately I have an even larger gun I will try today.
>> This would indeed explain whi I had variable startups I hope. Especially
>> when tuning the cap. For anyone of interest its 2-20pf johannson type. The
>> manual says 1.5-15.  Close enough.
>> Will update later on if I solve the oscillator problem.
> Good luck!
> I hooked on to the RF-feed and trimmed it for best response.
> Cheers,
> Magnus
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