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

James Meek JimMeek at sbcglobal.net
Thu Sep 22 00:51:06 EDT 2005

On Tue, 20 Sep 2005 01:13:50 -0700, Rex <rexa at sonic.net> wrote:

> On Tue, 20 Sep 2005 00:17:36 -0500, James Meek <JimMeek at sbcglobal.net>
> wrote:
>> Hmmmm.  I must have found by ohmmeter the connection between the eeprom
>> and the rubidium via J2-14A, not realizing they were both inputs (as I 
>> had
>> concluded that the pinout was non-standard).  I not sure about what I
>> found out about the connection of the rubidium serial output, but I seen
>> to recall that it doesn't just end electrically where it does visually,
>> but
>> rather "goes underground" through the inner layers of the board and
>> surfaces
>> elsewhere in the circuitry.
> I'm sorry. It's late and I don't really understand that. Please tell me
> what you have found connected by underground circuits or (possibly) by
> circuits that I have missed.

Sorry, it was nearly a year ago that I did the circuit tracing, and before 
could get down to being thoroughly systematic about it I was hit with an 
assignment at work that required me to abandon the project.

Hauling out the board and tracing around a little again, and reviewing the
messages, I see that the reasons for confusion were that I had not 
identified the functions of any lines except the 15V power and ground 
that I suspected the board of having an internal signal routing layer 
(which I now
conclude it does not), and I probably interpreted a resistance measured 
a sneak path through some semiconductor junctions and ground or Vcc as a 
path part of which was passing through a buried internal layer.  When you 
the dead-ending serial output line, what sprang to my mind must have been
a false memory that conflated the sneak path with the dead-ending signal 
which I suspected of having another connection through the imagined 
internal signal
routing layer.   Another factor was that, since I know that some other 
contain DDS circuits that are programmed through serial inputs, I was 
to find a connection from the serial eeprom output to the rubidium, and 
the fact
that I couldn't find a visible one made me believe all the more that the 
had more inner layers than just the ground plane.
Sorry to have misled you by voicing such inaccurate memories.

> I'm just trying to help here, and I _AM_ the person that figured out
> that the rubidium box needs 5 V. You could still be stumbling trying to
> figure why there is no output.
> Please be specific with any new knowledge or criticism of my help.

I certainly didn't mean any criticism.  Because I suspected the board of 
an additional, internal signal routing layer, I thought I had stumbled 
across a
connection not visible in the surface routing layers, which no one could 
expected to find unless they happened to connect across the same points.

> P.S. Have you tried to power it up with the info I just gave you.

No, because I have another project in progress, and put my original post
on the list only trying to be helpful to people who it seemed had bought
the units on the sawed-off board sections that had none of the peripheral
circuitry.  I'll power it up this weekend and let you know what I find.

> Give me some *facts* with new information or shut up. You are beginning
> to annoy me.
> And **** you very much for not thanking me in the previous message.

Pardon me for failing to thank you more effusively in my rushed reply.
But as I wrote, "Many thanks for this info.  I was reluctant to power up
the whole board, before doing further circuit tracing" (which I hadn't 
time to do).



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