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

nnovotney at cinci.rr.com nnovotney at cinci.rr.com
Thu Jan 10 16:35:31 EST 2008

Hi Jan---I got some of those ebay units just a month or so ago & got them running!!!  I can use my PC to adjust the freq/dds to whatever I want.

I don't have the info right here., as I am not at home now---but as I remember you ONLY need +15V & gnd  on the 1st 2 pins.  Pin 3 will shoe the lock stat (goes low after 4-5 minutes).  I think pin6 was the output...the trick is that it puts out 1 very narrow pulse (few microseconds) every second....so run it inot a counter or a digital scope.  You will not see it on a normal scope, other than seeing it trigger the unit.  You should try this to see that the unit is basically working.

To get the high MHZ freqs, tap into the "Rf" under the cover (on the DDS board).  The  black corner connector strip is indeed your pc connection...I'll  send details later as to the hook up.

---- Jan Fredriksson <jan at 41hz.com> wrote: 
> Hi time-nuts,
> It's an amazing list you have here! I had no idea! A new world to me.
> I am new here and this is my first posting.
> I recently got one of the Ebay FE-5680A units, originating 
> from a Motorola telecom board, without a coax out.
> I do not even have the Motorola board so there is little to 
> start with.
> I fund some postings on the FE unit, most from 2005, 
> here on in the time-nuts list.
> Did any of you make any progress with this unit and the 
> pinout and communicating with it?  I'd prefer not to fry the 
> thing right from the start..... 
> I have opened the lid and found that my unit has a RS232
> chip, Sipex SP233ACT. There is also a small internal 
> 5 pin connector on the PCB, connected to the RS323 
> chip Rx/Tx and +5V.
> I can trace the front panel 9-pin connector pin 1 / power in
> to the onboard VR and pin 2 is ground.  
> The unit has and a AD9830A DDS for frequency synthesis. 
> In the product sheet for the FE-5680A it's mentioned that the 
> unit can be factory programmed to wanted frequency. A good
> guess is that it's  via this PCB port as RS232 is not available 
> on the front panel connector as far as I can find.
> There are also two pushbuttons on one PCB. 
> I have seen mentioned in the datasheet that it's for trimming 
> the frequency. 
> Well, any input would be highly appreciated. I have searched 
> the net for all docs I could find but nothing very useful so far.
> I will be happy to share my findings if someone is interested.
> Neo-Timer Jan 
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