[time-nuts] HP Z3817A Reverse Engineering

Ed Palmer ed_palmer at sasktel.net
Sun Jan 8 19:28:03 UTC 2012


On 1/8/2012 12:19 PM, Azelio Boriani wrote:
> OK, I wasn't able to find anything else. Moreover the STLN4096A seems to
> have a Rb oscillator now from the usual 'bay vendor... so seems confusing
> as the Z3817A may be the E1938A mounted on the PCB that can discipline it
> or it is another type of unit or whatever else. No picture found until now
> using google.

Yes, I agree that it's odd. It appears that Motorola had the same part 
number for both the OCXO-equipped and the  Rubidium-equipped oscillators.

> Is the Z3817A like the fig.1 picture you can find here:
> http://www.prc68.com/I/HPE1938.shtml ?

No, the E1938A oscillator is the entire board shown on that page.  The 
board is the controller for the oscillator.  Without the board, I think 
that all you've got is a nice paperweight.  A while ago on the auction 
site, a vendor was selling just the crystal enclosure (the silver 
disk).  I wondered if it was even possible to put the enclosure on 
another controller or if the controller contained some tuning parameters 
that were specific to the enclosure.  He sold a few, did any time-nuts 
buy them?  Anything to report?

I forgot to take pictures when I had the unit apart, but the STLN4096A 
consists of the E1938A oscillator, a processor board, and a power supply 
board.  Here's what the OCXO version looks like from the outside:

http://gzwg.blogspot.com/2009/04/motorola-stln4096a-hight-remote.html

Actually, mine looked quite a bit worse than that one, but that's 
another story.

Just for completeness, here's what the Rubidium version looks like:

http://gzwg.blogspot.com/2011/11/motorola-stln4096a-rubidium-oscillator.html


Ed

> On Sun, Jan 8, 2012 at 6:57 PM, Ed Palmer<ed_palmer at sasktel.net>  wrote:
>
>> Hi Azelio,
>>
>> Thanks, but I already found that.  I've moved quite a bit beyond that.
>>   That message was  one of the few in the archives that had any significant
>> info on this unit.  For some reason, I find that surprising.
>>
>> Ed
>>
>>
>> On 1/8/2012 11:33 AM, Azelio Boriani wrote:
>>
>>> Have you already this?
>>>
>>>
>>>
>>> On the TIB (P1) DB-25 connector, I'm fairly confident about these:
>>>
>>> V+ pins 1 and 21
>>> V- pins 8 and 25
>>> 10MHz #1 pins 2/15 xfmr coupled, ~4.6V into 1M
>>> 10MHz #2 pins 23/16 xfmr coupled, ~4.6V into 1M
>>> 1PPS pin 14
>>>
>>> Supply voltage is dictated by Lucent DC-DC converter. Input is 18-36V,
>>> 1.9A.
>>>
>>> Still chasing down the other pins. Currently I am working on a possible
>>> disciplining input:
>>>
>>> input of some kind to U6/3 via 100 ohms pin 18, prob. diff with 4
>>> input of some kind to U6/2 via 100 ohms pin 4, prob. diff with 18
>>>
>>> The MMI (J1) DB-9 connector is RS-232, 9600baud, 8n1 and runs a a
>>> familiar SCPI interface.
>>>
>>>
>>>
>>> On Sun, Jan 8, 2012 at 6:20 PM, Ed Palmer<ed_palmer at sasktel.net>   wrote:
>>>
>>>   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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