[time-nuts] Question about the FE-5680A

Rex rexa at sonic.net
Thu Dec 12 21:23:34 UTC 2013


The FE5680A has about ten years of history on time-nuts. The FEI webpage 
bears little resemblance to most of the units that you will find. I have 
never seen one with a factory separate connector for oscillator output. 
Many needed both 15V and 5V to operate. Different versions have  outputs 
for PPS and/or (x)MHz (some can be programmed for output frequency). I 
don't think there are any markings on the various versions that clearly 
identify what, exactly, their features might be. Members here have 
hacked the internals to describe two basic evolutions of design.

I suggest you do some hours to weeks of reading and come back with any 
specific questions. Here are places to start...

The KO4BB Wiki -- http://www.ko4bb.com/dokuwiki/doku.php -- scroll down 
to find a couple of FE5680A links.

The time-nuts searchable archive -- 
http://www.mail-archive.com/time-nuts@febo.com/info.html -- put in 5680A 
or similar and get many many posts to read.



On 12/12/2013 5:24 AM, Sidney Cadot wrote:
> Hi all,
>
> I recently bought a second-hand FE-5680A for some light
> experimentation via ebay.
>
> There seems to be a number of variants floating around. Mine in
> particular lacks a J2 (where I would expect to see the 10 MHz
> connector), so I only have the DB9 J1 connector.
>
> The unit is working, If I supply 15V over DB9 pins 1/2, the unit heats
> up, after a while pin #3 drops to indicate a lock, and pin 6 shows a 1
> microsecond wide PPS that I am happy to see, since that is what I am
> most interested in.
>
> I have a few questions:
>
> * Does anyone else have a unit that lacks a J2 10 MHz output? Is the
> intention of such a unit solely to provide a PPS?
>
> * Is there a way to tell which revision/Option I have, eg.via inquiry
> on the serial port?
>
> My unit has no "Option" indication, all I have is FE-5680A / UN17491 /
> serial nr. 27727W / Revision: B.
> Without opening the unit at least, there are no other visible markings.
>
> * J1-1 has function +15V, J1-2 is "+15V return", which, as I
> understand it, means "ground" for the main power (I don't know how to
> interpret "provides DC return" other than that).
>
> However, there is also GROUND (J1-5), and there are at least the
> following signals:
>
>    - J1-3 Loop Lock Indicator (output; appears to be 5V, with 5V
> meaning "no lock")
>    - J1-6 Manual says "not used", but it carries a 1 us PPS (5V)
>    - J1-8 RS-232 Rx (input for the FE-5680A)
>    - J1-9 RS-232 Tx (output for the FE-5680A)
>
> Should I assume that pins 3, 6, 8, 9 are all in reference to the
> ground provided by pin 5?
> Is pin 2 only "ground" for the pin 1?
> Is there any relation between the voltage levels at pin #2 and pin #5?
>
>
>
> Any help is greatly appreciated!
>
> Sidney
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