[time-nuts] HP E1938

Richard Solomon w1ksz at outlook.com
Sat Apr 15 15:56:09 EDT 2017

Mention of the E1938 reminded me that I have a schematic that

measures 36" X 72" (yes, 3 feet by 6 feet) !! Talk about readability.

Also, somewhere, I still have one of them. I'll need to go find it and

try firing it up.

Now you got me going again ...

73, Dick, W1KSZ

Sent from Outlook<http://aka.ms/weboutlook>
From: time-nuts <time-nuts-bounces at febo.com> on behalf of Larry McDavid <lmcdavid at lmceng.com>
Sent: Saturday, April 15, 2017 10:42:40 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP E1938

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?


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.

Best wishes,

Larry McDavid W6FUB
Anaheim, California  (SE of Los Angeles, near Disneyland)
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