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

Wed Mar 14 11:56:29 EDT 2007

Dear Time Nuts,

This post was time ago.... but at this moment I'm working on my FE-5680. 
I had to replace a 74HCT74 IC inside the unit to get the 1 PPS out.
Now I'm wondering what the other pins are used for. As far as I have 
figured out now the following pins are used:

1   +15V
2   gnd
3   lock  low  = unlock high
4   n.c. (this unit has an internal +5 V logic to drive the 2^23 divider 
chain; this generates the 1 pps from the 8,.... MHz)
5   gnd
6   1 pps out
7   ?
8   ?
9   ?

Inside I find a small PCB directly behind the DB-9 connector. I guess 
this is a smart C-field adjustment. It has three wires going to the 
motherboard. +5 V, Gnd and an analog voltage. I guess this voltage is 
slowly varied over the lifetime of the unit by using an internal 
counter/clock, to adjust the C-field.

Just curious about the knowledge which is accumulated in the Time-Nuts 
community about these units...

Best regards, Jeroen

Rex wrote:

>On Sun, 18 Sep 2005 15:52:03 -0500, James Meek <JimMeek at sbcglobal.net>
>wrote:
>
>  
>
>>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.
>>
>>JM
>>    
>>
>
>Here's what I worked out for the pins on the DB-9 on my5680A...
>
>1   +15V  near 2A initially, dropping to about .8A warm
>2   gnd
>3   lock  high = unlock
>4   +5V   about 160 mA
>5   gnd
>6   1 pps out
>7   10 MHz out
>8   RS-232 Rx  (into rubidium)
>9   RS-232 Tx  (from rubidium)
>
>The initial impression from the seller was that only 15V was needed. The
>info on the FEI pages don't mention needing 5V in any option. A lot of
>the pin functions are different from any description I have seen.
>
>I think I have the same full board you have. I looked at it back around
>the beginning of the year. If I remember right, the RS-232 pins of the
>rubidium get fed from off-board signals. I did power it up using this
>board once. There is a dual color led at the edge of the board that
>indicates lock state, if I remember right.
>
>Does your board have a sticker on it somewhere that says: SGLA4000B High
>Stability Osc Assembly?  After lots if web searching, I figured that
>this seems to be part of older Motorola Cell equipment. I found a site
>that says they repair them. I tried sending an email asking if they have
>any documentation, but got no reply.
>
>Maybe later I can find time to scan the board. What I remember from the
>hacking I did, was that there didn't seem to be anything intelligent
>going on on the board. I don't remember any details though, maybe I
>missed something.
>
>Oh, on the side of the rubidium there is an adjustment screw. I thought
>for sure this would adjust the C-field and hence the freq, but I don't
>see any result by turning this. No idea what it is for.
>
>I tried all sorts of things sent to the serial port but never saw any
>effect or reply. I tried this at various baud rates. I also scoped the
>other side of the MAX3232 chip inside, so I know the data was getting in
>there.  The other port of the MAX3232 is connected too. It goes to what
>must be a maintenance header inside. Nothing interesting came from
>trying that port too.
>
>So, if you feed it both 5V and 15V, I'd bet your unit will come up and
>give you 1 pps and 10 MHz. If, like mine, the frequency is a little bit
>off, it sure would be nice to know how to adjust it.
>
>-Rex, KK6MK
>
>
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>time-nuts at febo.com
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>
>
>  
>

-- 
Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

Phone: +31.15.27.86542
Fax: +31.15.27.85755
E-mail: J.Bastemeijer at TUDelft.nl
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