[time-nuts] Odd HP 117A configuration

Scott McGrath scmcgrath at gmail.com
Thu Sep 11 11:32:29 EDT 2008


Hi Russ,

Yes i did and it was a marvelous hack in the best sense of the word,
It was fascinating to see how this actually worked, it of course is no
longer necessary and I have removed it in favor of protecting the A1
assembly fully within the chassis.

My 117A is a Prefix 438A unit and my manual covers 525A and below.
I'm still debating whether to use a AMRAD antenna and disconnect the
+35 from the antenna (by installing a jumper block for reversability)
or find the proper 10509A loop antenna for authenticity.    I have
been offered a amp assembly for the antenna by another member so I
have thought about fabricating the actual loop assembly but I do not
have dimensions for the loop itself which looks to be center tapped
which also would  the tube which bisects the loop.

I bought this a decade ago and was only able to find a manual recently
always kept it because I knew how rare this unit is.    Right now it's
been recapped (electrolytics) and I have replaced the chassis mount
transistors BTW a NTE121 will replace the TO-3 pass transistor if that
has given up the ghost.    RIght now I am going through the power
supply board A9 and replacing the resistors many of which have changed
value after physically rebuilding the PCB which had a 1/2" hole burned
in the area of R2-4.    One of the challenges of recapping is that
electrolytics are now much smaller for equivalent ratings so a lot of
teflon sleeving has been used to prevent potential short circuits.

So much fun to be had with this stuff!

- Regards Scott

On Thu, Sep 11, 2008 at 10:50 AM,  <wa3frp at aol.com> wrote:
>
> Scott,
>
> Good luck on the rare 117A.
>
> Did you get my e-mail with attachment containing the pages of the manual for
> your updated unit?
>
> Russ
>
> -----Original Message-----
> From: Scott McGrath <scmcgrath at gmail.com>
> To: wa3frp at aol.com
> Sent: Wed, 10 Sep 2008 12:42 pm
> Subject: Re: [time-nuts] Odd HP 117A configuration
>
>
>
> Hi, Ross
>
> Please - It would be interesting to see how this worked.   From the
> date codes on the components my 117A was  built in late 1964 - date
> codes on conversion module date from 1968. As Tom noted it is a
> interesting historical footnote from use of the atomic timescale to
> UTC timescale with leap seconds.     And now due to the influence of
> embedded device manfacturers who want 'cheap n cheerful' firmware we
> are now discussing doing away with leap seconds.    Interesting how
> the pendulum of historical trends oscillates.
>
> Right now the 117A is having all the electrolytics replaced while I am
> reconstructing the PS module trace by trace
>
> - Scott
>
>
>
> On Wed, Sep 10, 2008 at 7:43 AM,  <wa3frp at aol.com> wrote:
>>
>> Scott,
>> I had a chance to look at my HP 117A manual last night and saw that
>
> your
>>
>> configuration is described there.  If it is not described in the HP
>
> 117A
>>
>> manual that you have, would you like me to copy those pages and send
>
> them to
>>
>> you as an attachment?
>> Russ
>>
>>
>> -----Original Message-----
>> From: Scott McGrath <scmcgrath at gmail.com>
>> To: time-nuts at febo.com
>> Sent: Mon, 8 Sep 2008 3:50 pm
>> Subject: [time-nuts] Odd HP 117A configuration
>>
>>
>>
>> All,
>>
>> I purchased a 117A at a hamfest years ago and am just now looking into
>> it.     This 117A is a bit different from the ones in the manual and
>> in pictures up on the web as it incorporates a telechron reduction
>> motor installed in fthe area in front of the TRF module harness
>> connector.     Had not looked at this unit much as I did not have a
>> manual which I now have as the power supply board (A9) had a charred
>> hole blown in it.     The TRF module does not insert fully into the
>> chassis due to the presence of the clockwork module.    Interestingly
>> enough the clockwork looks like HP installed it or someone did a VERY
>> good job.  Does anyone know what this clockwork is intended for?
>>
>> I am now rebuidling the circuit board with glass filled epoxy (West
>> Brothers + microsphere filler) with a mold/retaining dam made from
>> silicone rubber.
>>
>> Also back when I was at UNH when I was young and foolish a HP 117A was
>> my introduction to precision timing as Jim Williams in Demerrit Hall's
>> maintained the frequency standard which consisted of a HP117A and a HP
>> 5245M frequency counter along with a decade worth of recorder output.
>>
>> _______________________________________________
>> 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 mailing list