[time-nuts] Symmetricom X72

[paul swed]

The lamp oscillator should not have an affect. It just excites the lamp. I
did see in you picture some very complicated FPGA class chips. I would
expect the photocell/diode to hit an opamp. Though maybe thats in the FPGA.
On the face of the lamp when off and shining a light do you see a black
film? Not uncomment for the rubidium to plate onto the glass and
essentially dim the emitted light. It can be recovered if that is the case.
Regards
Paul.

On Mon, Aug 10, 2020 at 12:40 PM Germán Herrera <g.herrera at ses.com.ar>
wrote:

> Hi Paul,
>
> First of all, thank you for your advice.
>
> I did try with the cover on, and also with the magnetic shield on (which
> consists of about three sheets of mu metal wrapped around the resonator
> cavity over and below the board (you can see the slits on the bigger
> board, on the pictures).
>
> I've had mixed results, with the unit warmed up but without the cover, I
> had the opportunity to have it locked for quite some time (about 8
> hours) before powering it off again. Other times it doesn't lock. Other
> times where the unit starts cold, after a couple of minutes locks for a
> short (~30s) time and gets back to sweeping frequency (unlocked state).
> I've seen that happen on an Efratom FRK with a defective resonator
> thermistor, that's why my main suspect is the temperature.
>
> I still have pending to attach the scope to the photodector amplifier to
> check if I see the modulation signal. After that I think it all goes
> digital so there's nothing much I can do. I did try varying the lamp
> oscillator frequency but didn't notice any effect (kind of a long shot
> since I don't know the right frequency), so I left it as it originally
> was.
>
> Kind regards!
>
> ---
> Germán Herrera
> Responsable IT
> Ingeniería
> SES Sistemas Electrónicos S.A.| Espinosa 1045 (C1405AMM) | Buenos Aires
> | Argentina
> W: +54 11 54538426 | Email: g.herrera at ses.com.ar
>
> On 2020-08-10 10:21, paul swed wrote:
> > German have you tried with the cover back on?
> > The external light in your picture could be affecting the system.
> > The color of the RB lamp looks about right and its nice and bright.
> > Also most Rbs I have worked on tend to insulate the various ovens and
> > such.
> > Temperature matters.
> > Regards
> > Paul
> >
> > On Mon, Aug 10, 2020 at 9:15 AM Germán Herrera <g.herrera at ses.com.ar>
> > wrote:
> >
> >> Hi everyone
> >>
> >> This is my first post on the list, tought I've been subscribed for
> >> some
> >> time.
> >> I'm in the process of troubleshooting an X72 which recently started to
> >> be unable to acquire lock. I've searched online for pics of this
> >> standard and wasn't unable to find anything, so i took some nice
> >> pictures which I'd like to share with you:
> >>
> >>
> >>
> https://drive.google.com/drive/folders/1HN8dms5CxPwUjdckEux2fOVTF5IoaI5u?usp=sharing
> >>
> >> After disassembling it I found that an optical filter which is
> >> supposed
> >> to be glued to the light path of the lamp was loose inside the unit. I
> >> attached it again but the issue persisted.
> >>
> >> If anyone is able any information about the thing (such as lamp
> >> working
> >> temperature, resonator temperature, lamp excitation frequency, etc..)
> >> I'd be grateful. It's sad that Symmetricom's manual is not able to
> >> provide any useful details.
> >>
> >> Cheers!
> >>
> >> --
> >> Germán Herrera
> >>
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