[time-nuts] HP Z3817A Reverse Engineering

Azelio Boriani azelio.boriani at screen.it
Sun Jan 8 17:33:22 UTC 2012


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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