[time-nuts] HP Z3817A Reverse Engineering

Ed Palmer ed_palmer at sasktel.net
Sun Oct 27 20:54:09 UTC 2013


Hi David,

Skip Withrow and I were able to figure out the connections and the basic 
operational features.  I've attached a document that describes our findings.

I wouldn't mind picking up another E1938 oscillator, but I'm reluctant 
to buy one that might have mismatched oscillator and circuit board (i.e. 
the serial numbers don't match).  I've asked a couple of vendors if the 
serial numbers matched, but they won't respond.  Does anyone have any 
experience with a mismatched combination?  How's their performance?

Ed

On 10/27/2013 1:26 PM, David Hooke wrote:
>
> Hi Ed,
>
> My E1938 also came from a very battered STLN4096A from the same 
> source, and I might also try to get the other boards functional. Could 
> you share the details of the GPS connections, and which GPS receiver 
> you used?
>
> Cheers,
>
> david
>
>> I recently purchased a Motorola STLN4096A with the HP E1938A 
>> oscillator.  I bought it for the oscillator only.
>>
>> Then I got intrigued by the HP Z3817A GPSDO that's included. I've 
>> reverse engineered most of it and I've got it running.  The 1 PPS is 
>> really good ( 1000 measurements, Std. Dev. of <200 ps, min to max 
>> range of <1.5 ns) and the HUP is very slowly dropping (currently at 
>> 13 us after ~1.5 days) as the oscillator works out the kinks after 
>> it's long sleep.  It's dropping much slower than my Z3801A did when I 
>> first turned it on.
>>
>> There's one input that I haven't been able to figure out.  I've got 
>> data in and 1 PPS in from the GPS receiver.  Everything seems to be 
>> working so I'm at a loss what that the other input could be for.  
>> There are no clues to it's function because it appears to go into one 
>> of the Xilinx chips.
>>
>> Does anyone have any more info on the unit?  Has anyone figured out 
>> the other input?
>>
>> I have searched the net and the archives.  There's very little info 
>> or discussion on this unit.
>>
>> Ed
>>
>>
>
>
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