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

Rex Allers rexa at sonic.net
Wed Mar 14 19:21:27 UTC 2007


On Wed, 14 Mar 2007 16:56:29 +0100, you wrote:

>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...
>

This doesn't really help much, but all units labeled FE-5680A are not
the same. As you see in the copied messages, a couple of us here
bought a few about two years ago. They didn't work. Eventually I
figured out that the ones we had needed +5 V on one of the pins in
addition to the +15 V. The data sheets on the FEI site didn't mention
this as a possibility. We never found a way to program ours through
the serial interface. Apparently other versions do respond to serial
commands. Sounds like yours may be one of those. 

So the bottom line is that good information for one unit may not apply
to another. I know of no way to tell except trial and error. I don't
think anyone here has had any luck getting detailed information from
FEI about any of their products.

-Rex


>
>
>
>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 mailing list
>>time-nuts at febo.com
>>https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>
>>
>>  
>>





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