[time-nuts] R&S XSRM Rubidium

paul swed paulswedb at gmail.com
Sat Jan 22 18:03:39 UTC 2011

Took the oscillator board apart last night and found C11 has a cold solder
joint. 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.

On Sat, Jan 22, 2011 at 6:35 AM, Magnus Danielson <
magnus at rubidium.dyndns.org> wrote:

> On 01/22/2011 04:19 AM, paul swed wrote:
>> Actually there is a paper by Arthur Molenkamp (Spelling wrong) thats quite
>> detailed and he seems to have done the same thing I am. You do not need
>> the
>> heater to start the RB lamp.
>> I have found 2 things this evening on the FRS-c.
>> The oscillator is intermittent and I might guess its the variable tuning
>> cap. Boy is that going to be a pain to pull. But bias voltages and xsistor
>> behavior look good.
>> Other item
>> Indeed there is a silver dot about 1-2mm in the Rb lamp capsule. I might
>> guess this is Magnus's RB that he reheated. I need to peel the glass/mica
>> cover off and believe the ampule is released from its holder by breaking
>> the
>> epoxy that holds it.  Really dislike that idea.
>> Magnus might the mica cover be removed and the capsule heated in place?
>> The
>> surrounding area seems to be teflon.
> Mine was sitting in a metal holder with some white soft material in between
> that I didn't identify. Since it needs to handle the temperature of 108
> degrees over long time I figured that it would survive my operation so I
> never bothered to pull the glass ampoule out of that grip since it was not
> coming loose easily. I haven't been inside a FRS-C so I don't know it looks.
> Recall that it is not very high temperatures which is needed.
> Cheers,
> Magnus
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