[time-nuts] HP E1938
Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun Apr 16 03:11:45 UTC 2017
More precisely the active EFC range is +1.25 to +3.75V with an absolute minimum of 0V and an absolute max of +5V.
At least this is the range that the pseudo differential AD7714 ADC inputs monitoring the EFC are configured for.
Bruce
> On 16 April 2017 at 14:57 Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
>
>
> 0 to +5V dc max, however only the 0 to 2.5V range appears measurable by the AD7714 ADC on the PCB.
>
> Increasing the EFC voltage decreases the capacitance in series with the crystal requiring an increase in the inductance exhibited by the crystal hence requiring a lower oscillator frequency.
>
> Bruce
>
> > >
> > On 16 April 2017 at 13:01 Larry McDavid <lmcdavid at lmceng.com> wrote:
> >
> > The units now available on eBay have various types of D-Subminiature
> > connectors and can be on either side of the board. I will have to wait
> > until my unit arrives to see what I get. It should be possible, if
> > necessary, to remove the connector and replace it with a more convenient
> > D-Submin connector on the desired side of the board.
> >
> > I did not originally note the additional zip'd info available from that
> > eBay website but now have those files. Thanks for that link.
> >
> > So far, I have not seen any spec for the EFC voltage and polarities used
> > in the "Integrated PWB." Anyone know that?
> >
> > The "full instrument" version also available now on eBay is a complete
> > GPSDO but at $130 plus $80 shipping. I really don't need yet another
> > GPSDO but would use the integrated PWB assembly for a low ADEV
> > free-running 10 MHz source. I have a HP 10811D for that now but will
> > evaluate this new unit for performance.
> >
> > Anyone have experience doing this and know the EFC requirements?
> >
> > Larry
> >
> > On 4/15/2017 4:01 PM, Richard (Rick) Karlquist wrote:
> >
> > > > >
> > > It's been 20 years, but I will try to recap what I remember
> > > about this connector. I believe there were 3 customers,
> > > and one of them required the DB connector with coax inserts
> > > for reasons of backward compatibility. I think this
> > > vendor was Motorola. We did not actually use the coax
> > > inserts, but left them blank and ran the RF, etc on
> > > ordinary pins. I believe you can make an ordinary male
> > > DB-25 mate with these insert versions by clipping off some
> > > of the pins that would be blocked by the female insert
> > > version. I vaguely remember that the other 2 vendors
> > > used gender changers or something. There might have
> > > an issue with the mating plane location being different
> > > for different customers.
> > >
> > > I am sure that time-nuts, being talented at repurposing,
> > > will be able to think about this problem and come up with
> > > a simple solution to interfacing with these boards.
> > > No need to buy insert type connectors. I never had
> > > any trouble making cables that connected to these units
> > > using plain vanilla DB25's.
> > >
> > > Rick N6RK
> > >
> > > On 4/15/2017 10:42 AM, Larry McDavid wrote:
> > >
> > > > > > >
> > > > Ok, so a standard DB 25-pin socket-contact connector will mate with the
> > > > on-board connector with the center hole and missing pins. That's good!
> > > >
> > > > I now notice a comment on your webpages about this device in which you
> > > > mention a schematic. Do you have a schematic of this board? If so, can
> > > > you point to it or send me a copy.
> > > >
> > > > I was unaware of the complete packaged unit on eBay; thanks for that.
> > > >
> > > > Another poster mentioned the wiring of the connector on the full
> > > > instrument version power connector; is that pin-out and spec available?
> > > >
> > > > Larry
> > > >
> > > > On 4/15/2017 5:05 AM, Tom Van Baak wrote:
> > > >
> > > > > > > > >
> > > > > > > > > > >
> > > > > > I purchased one of these HP E1938 OCXO recently on eBay but have not
> > > > > > yet
> > > > > > received it.
> > > > > >
> > > > > > Is that special D-Submin connector a receptacle-shell, pin contact
> > > > > > version? Will a standard plug-shell, socket contact 25-pin D-Submin
> > > > > > fit it?
> > > > > >
> > > > > > > > > > >
> > > > > Hi,
> > > > >
> > > > > I'll cc the group here since we may get some useful comments.
> > > > >
> > > > > I'm not exactly sure what you mean. The E1938A oscillators that I've
> > > > > seen and tested look like this:
> > > > >
> > > > > http://www.leapsecond.com/museum/e1938a/
> > > > >
> > > > > And those can be interfaced with a simple D-sub DB25 connector on the
> > > > > PCB. For connections, see that page, or any number of postings about
> > > > > the E1938 in the time-nuts archives.
> > > > >
> > > > > Note that on eBay there are at least three variations of E1938A
> > > > > oscillator. The item#'s below are just random search picks (I have no
> > > > > affiliation with any buyers or sellers) and I also know not all
> > > > > surplus refurbished surplus recycled surplus stuff works. But we do
> > > > > this because when they did work, they are sometimes totally amazing.
> > > > >
> > > > > 1) There's the bare "puck" alone, as in
> > > > > http://www.ebay.com/itm/290829077542 -- and I have no idea where one
> > > > > would start with that item since all the support circuitry on the PCB
> > > > > would have to be re-created by hand.
> > > > >
> > > > > 2) There's the integrated PCB assembly, as in
> > > > > http://www.ebay.com/itm/181043193416 -- which is more like what I
> > > > > tested.
> > > > >
> > > > > 3) There's the full instrument version, as in
> > > > > http://www.ebay.com/itm/171293069062 -- which is most likely to work,
> > > > > or be less hacked up, or dented, or salvaged, or rusted. It even has
> > > > > all the connectors and power supplies, and GPS, etc.
> > > > >
> > > > > If any other time nuts have experience with each of these methods to
> > > > > obtain a E1938 oscillator, please let us know.
> > > > >
> > > > > > > > >
> > > > _______________________________________________
> > > > time-nuts mailing list -- time-nuts at febo.com
> > > > To unsubscribe, go to
> > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > > > and follow the instructions there.
> > > >
> > > > > > >
> > > > >
> > --
> > Best wishes,
> >
> > Larry McDavid W6FUB
> > Anaheim, California (SE of Los Angeles, near Disneyland)
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
> > >
More information about the Time-nuts_lists.febo.com
mailing list