[time-nuts] FEI FE-5680A Rubidium Pinout

Brooke Clarke brooke at pacific.net
Sun Sep 18 17:11:48 EDT 2005

Hi James:

Would it be possible for you to put the board on a flat bed scanner and 
if it's too big to fit all of it, then the part that has the 5680 and 
the related EPROM and make a color scan at 600 DPI?  Also a similar scan 
of the back of the same area and email it to me?  (large attachments are 
not allowed on the list and these files might be 30 MB each.


Brooke Clarke, N6GCE

w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml

James Meek wrote:

> I've just found the time-nuts mail list, and the threads
> concerning the programming of the FEI FE-5680A rubidium
> frequency sources that some have bought on ebay and been
> unable to program.
> I, too, bought one of these from an internet source last year
> (a different source from the one mentioned in the thread I found),
> and was unable to get anything out of it by simply powering it
> up and connecting to it through its 10-pin interface using the
> pinouts for a standard FE-5680A.
> However, mine did not come naked or on a cut-off section of PC board
> like those I've seen advertised on ebay since then.  Rather, it
> came attached to a large board containing several voltage regulators,
> a serial interface buffer, a serial EPROM chip, and some other logic.
> Although I have not yet found the time to fully analyze the
> circuitry, it appears to have been set up so as to program the
> FE-5680A from the serial EPROM.  I have no idea whether it needs
> to receive a command from an external source to initiate that
> programming, or whether it happens at power-on (perhaps with the
> clocking of the serial EPROM by the FE-5680A itself?).
> I read that Rex and Brian Kirby have figured out that the unit needs
> a +5V supply (or perhaps just a logic input) in addition to
> the 15V supply in order to get any output.  If someone could
> provide me with specifics on that and anything else they've discovered
> about this part, I'd have a lot more incentive to try to figure
> out what the EPROM does -- and of course would share my findings
> with all here.
> JM

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