[time-nuts] HP Z3817A Reverse Engineering

Robert Benward rbenward at verizon.net
Mon Jan 9 14:58:00 UTC 2012


Hi Ed,
I just tracked down Fluke and he offered me one, and per your advice I will 
try and confirm the condition before purchasing from him (not that there are 
alternate sources) .  I have the schematics, but taking apart the hocky puck 
is another matter, I pry and pry but get nowhere.    I don't think it was 
designed to take apart.  What buggs me is that if I warm up the oven and 
stimulate the oscillator with an external signal, it will oscillate.  So it 
DOES work, and if I go into the puck to trouble shoot it, I probably won't 
find anything defective.

Bob



----- Original Message ----- 
From: "Ed Palmer" <ed_palmer at sasktel.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Sunday, January 08, 2012 10:07 PM
Subject: Re: [time-nuts] HP Z3817A Reverse Engineering


> 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 ?
>
>
> 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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