[time-nuts] Re: FE-5680A Adjustment board

[Luca Pandolfini]

Hello everyone,

Thank you very much for your interest, as well as for the many links and
book recommendations. I had actually come across many of them before,
but only had the chance to skim a few chapters (mainly the physics
primers...).

Here you can find a Google Drive folder containing everything I’ve
managed to put together so far. I intended to document things more
thoroughly, but in the end I decided to share the material in its
current form, also because (due to work and family business) I won't
have a lot of time to spare for additional experimentation in the next
few weeks... However, I hope it’s already useful!

If anything is not clear (or wrong!), I’d be very happy to discuss it
here. I’m also genuinely curious to hear your feedback. (BTW, I set the
folder permissions in such a way that it is possible for everybody to
comment on the files; even though most of them will be better visualised
after downloading them...). For me, it was a lot of fun! I hope this
might also be useful for the community.

A couple of notes of caution:

i) Regarding the "Version": my photos aren't great, but they should be
sufficient to document the exact layout of the device (an FE-5680A with
two separate daughter boards: the DDS and the "Adjustment Board", each
with its own serial interface). I also included the serial number and
board versions, and the level of detail should be reasonable. BUT if you
have specific questions I can further clarify this point (as far as
possible provided that I don't have to take apart the bottom of the
mainboard).

ii) On my unit, the serial interface of the “Adjustment Board” was not
connected to the output port, and the serial-to-TTL chip was not
powered. To communicate with it, I had to jumper with solder a pad near
the 5-pin socket where the TX/RX pins are located (see photos). It is an
obvious check, but worth the effort! ;)

iii) Among the available serial commands, I’ve only tested the "read-
only" ones, which are safe and cannot corrupt the EEPROM. The remaining
commands look sensible based on the disassembled code (and anyway this
is relatively safe having a backup EEPROM dump), but I haven’t tried
them myself. So please proceed at your own discretion.

Thanks again, and I look forward to know your thoughts!

Luca

https://drive.google.com/drive/folders/1mYLdO_0REFF_YGkyJYDhlpBa10ILOVw4?usp=sharing


> Hi Luca,
> 
> Â > since it looks like a device becoming obsolete...).
> 
> That's never been a deterrent to time nuts; we live for eBay specials:
> the cheaper, older, obsolete, the better. In particular the FE 5650A
> and 
> 5680A are a favorite here because so many have been available on the 
> surplus market, thanks to upgrade cycles in the telecom industry. Your
> project & contribution is very welcome. See also:
> 
> 1) The most detailed document on the FE 5650A ever written. Not just
> an 
> article, more like a book, donated to time nuts, by Michael Parker
> (324 
> pages):
> 
> http://leapsecond.com/u/parker/ParkerIntroRFS-PPCP.pdf
> 
> 2) The best introduction to Rb from a physics and design perspective 
> (163 pages), by Bill Riley:
> 
> http://www.wriley.com/Rubidium%20Frequency%20Standard%20Primer%20102211.pdf
> 
> 3) Also by Bill Riley, a thorough history of Rubidium clocks (35
> pages):
> 
> http://www.wriley.com/A%20History%20of%20the%20Rubidium%20Frequency%20Standard.pdf
> 
> /tvb
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