[time-nuts] Symmetricom X72

[Germán Herrera]

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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