[time-nuts] FE-5680A pinout

Rex rexa at sonic.net
Sun Sep 23 16:45:08 EDT 2007

Stan W1LE wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+rexa
> Hello Jose,
> Try:    http://www.freqelec.com/prod_pdf/FEI%205680A%20Rb.pdf
> Frequency Electronics Inc.  =  FEI
> This .PDF may shed some light.
> Be sure of the options you have. base unit has 15 VDC, other options use 
> a different voltage
> for power.
> May have to go inside and solder a coaxial cable, to get the Ref. output 
> outside.
> If you need more help, send an email to the factory info desk.
> They were quite helpful to me.
> Stan, W1LE   FN41sr   Cape Cod
Seems there are lots of versions of the FE-5680A. Several of us bought 
versions a few years ago that did not match other known information 
(like the link above).

Here is a link to a message I posted back then about what I had learned 
by digging into my unit:

The ones we bought needed 5V in addition to 15V into the DB9 to operate. 
The 10 MHz output did come out on one of the pins on that connector. I 
think that output pin did match the general information.

In spite of the fact that tracing circuits on the board showed RS-232 
I/O pins on the DB9 and also on an internal header, and with several 
people searching for information, we never did figure out any way to 
adjust the frequency of our versions of the FE-5680A.

Stan's, post that he actually got a helpful response from FEI seems 
contrary to our attempts back then. I just did a quick browse of their 
web pages today and got a bunch of circular links that never produced an 
email address that looked like it might be worth a try. Maybe I missed 
something. Stan, care to share any pointers on how you found this 
'factory info desk'? I'm not trying to be sarcastic, just wondering, 
because everyone got blown off, back then, when we were looking for any 
clues on our units.

My impression of FEI is that they, like many other companies, cannot be 
bothered with talking with anyone who has not, or may not, give them 
lots of money. That is certainly their right, doesn't mean I like it. 
Also, it may be possible that if you find the right person, you might 
actually get good help. I did that with a different company a while 
back, by finding an engineer who helped a lot, and then later got a 
delayed reply from someone else telling me they had no time to tell me 
about old units, but if I would want to buy a few thousand to my specs 
they would be happy to help.

So, for the OP, there seem to be many versions of  these units, all 
labeled FE-5680A. There seems to be no absolute answer on pin-outs. If 
you are lucky, your unit will match one of the published configurations 
and be adjustable using RS-232 command sequences. For the ones we found, 
we only got them operational by reverse-engineering (results in the 
archive link), and I have never found any way to get mine really exactly 
enough on 10 MHz even though other units seem to be programmable, using 
published command sequences, over a wide range of frequencies.

-Rex, KK6MK

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