[time-nuts] HP Z3817A Reverse Engineering

[Azelio Boriani]

I had a negative experience with chinese vendors too. Bought a Z3815A, yes
works, the GPS unit has heavy rust and the boards shows sign of exposure to
high humidity if not rain. Fortunately the E1938A oscillator seems clean
and works OK. From fluke I got an LPFRS very different from the pictures
and inside there was heavy traces of past rust accumulated on the PCB. He
sent another but it is not so much different, only a bit better. On the
other hand the GLONASS receiver from fluke is perfectly OK.

On Mon, Jan 9, 2012 at 4:07 AM, Ed Palmer <ed_palmer at sasktel.net> wrote:

> Hi Bob,
>
> I bought mine on eBay from fluke.l for about $114 (including shipping).  I
> don't know if he has any more.
>
> He didn't get positive feedback from me.  His pictures showed a
> reasonable, used unit.  The unit he shipped was dented badly enough that it
> was slightly crushed and appeared to have been out in the rain.  It does
> work, but the E1938 seems to be taking a long time to settle down.  I hope
> the crystal wasn't damaged when it took the hit that dented the case.
>  There is no physical damage to any of the boards.  I've dealt with him
> before and was surprised and disappointed that he didn't describe the
> condition better.  Buyer beware.
>
> As for your 'lazy' E1938, have you grabbed the schematics and circuit
> description from
>
> http://www.prc68.com/I/**HPE1938.shtml<http://www.prc68.com/I/HPE1938.shtml>?
>
>
> Ed
>
>
>
> On 1/8/2012 5:58 PM, Robert Benward wrote:
>
>> Hi Ed,
>> May I ask where did you get your STLN4096A and what you paid for it?  Do
>> they have any more?
>>
>> My E1938 recently crapped out.  If I put a substitute 10MHz near the
>> first buffer, the PIC processor comes alive, then I can remove the 10MHz
>> and it begins to oscillate on it's own.  I can quickly recycle power and it
>> still oscillates.  Let it cool down and I need to repeat the "stimulus"
>> procedure. Anybody have any ideas?
>>
>> Thanks,
>> Bob
>>
>> ----- Original Message ----- From: "Ed Palmer" <ed_palmer at sasktel.net>
>> To: "Time-Nuts" <time-nuts at febo.com>
>> Sent: Sunday, January 08, 2012 12:20 PM
>> Subject: [time-nuts] HP Z3817A Reverse Engineering
>>
>>
>>  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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