[time-nuts] FEI5680A Rubidiums On Ebay

[Rex]

On Thu, 15 Sep 2005 16:21:51 +0200, Jeroen Bastemeijer
<J.Bastemeijer at EWI.TUDelft.nl> wrote:

>By the way, did someone look into the type-number of the DDS? Or is it a 
>custom build "discrete" DDS?

The FEI5680A uses an AD9832. There is also a Xilinx in it and a couple
other big ICs. The output on the one I bought is 1 PPS and 10 MHz. The
FEI web page specs a frequency of 1 to 20 MHz and programmable to 1 x
10^-13. FEI has not been friendly in giving any more info.

The eBay seller claimed that the unit needed 15V and that info on the
FEI web pages described the connector. After returning one, I did a some
reverse engineering and figured out that this unit needed 15V *and 5V*
to run. I think I have figured out the pins on the D connector, and it
does not exactly match the info on the FEI site.

Seller claims other satisfied buyers, but I can't imagine how they
figured out how to use it unless they have access to some Motorola
documents. (It seems it was use in Motorola equipment.)

There is a MAX3232 serial chip in it that connects to the D connector.
The seller claimed originally that they programmed like the 5650A, but
this is not true. Nothing I ever sent to it on the serial lines ever
elicited any response or reaction from the unit. 

Mine is not exactly on frequency (10 MHz) so it would be nice to have a
way to adjust it.

Here is part of a message I posted after my crusade to figure this thing
out in January...

---

To get to the point... by digging at circuits, I eventually figured out
they needed +15 V but also +5 V on a different pin. With the two
voltages, mine now came up giving 1 PPS and also 10 MHz on a different
pin.

I have worked out that RS232 Tx and Rx signals (from a MAX3232) come out
to two pins on the external DB9 connector. I had expected it would
program like the 5650 as described here:
http://www.leapsecond.com/museum/fei5650a/
Thus far, I haven't seen any reply to anything I send to the unit on the
RS232 pins.

So, either these units are not programmable or I just don't know how to
talk to them. I have not found any documentation on how to program the
5680A. Does anyone have access to any more information. Did Don Latham
work out his published information about the 5650 by logic and guess
work or did he have access to something more?

I wanted to try all other sources of information before contacting FEI
as I have heard they are not that friendly unless money is involved.

If it helps, this FE 5680A rubidium was used on a Motorola SGLA4000B
High Stability Oscillator (HSO) that was (I think) used in cell sights.

-Rex