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

James Meek JimMeek at sbcglobal.net
Sun Sep 18 16:52:03 EDT 2005

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.


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