[time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

[paul swed]

Well we are kicking butt on 723 oscillators. I have the 1000 hz model and
found it at the MIT flea about June.
Bad rectifier section. Cap was good though I carefully reformed it. Have to
say what attracted me was the case and then the realization of what it was.
It works very well so now I can make sure my cesium is on frequency.
There is a schematic online but its a picture actually in the wood case. I
copied that as I could find no real details.
I do have the genrad article.
The actual internals are hot. Be careful. It uses an output transformer as
the only isolation.
It makes sense actually. It keeps the 60 Hz magnetics out of the oscillator.
I thought my tube might be bad as it didn't glow. But its a 1.5 V filament
ohm'ed it out and it was fine.
Lastly I have a hacked power cable. I was going to buy the right plug. But
it actually is a bit unclear. It should be the cenetr ground and they are
around $15 each. Its not the cost. The 3 I see are sort of unclear that
they match my socket.
I swear I actually have one. Some place here.
Regards
Paul
WB8TSL

On Sat, Dec 9, 2017 at 10:30 AM, Eric Scace <eric at scace.org> wrote:

> Another fascinating tuning-fork standard was used together with a
> Synchronome to govern the timing of pulses of Morse code on undersea
> telegraph cables in the British empire’s globe-girdling telegraph network.
> Timing was derived electromagnetically from incoming Morse code signals (a
> bi-polar signal where one polarity represented a dit and the other a dah,
> but both dit and dah were of equal length) to set the master at each
> downstream relay/switching station on a cable route.
>
> In essence, brass, mahogany and electromagnetics were use to perform all
> the functions done today on fiber optic cables: signal generation,
> multiplexing, regeneration, and timing recovery… not to mention encoding &
> decoding plus printing.
>
> One can see a working example at the Museum of Undersea Telegraphy in
> Porth Curno, Cornwall — a museum well worth the detour to Land’s End.
>
> — Eric
>
> > On 2017 Dec 09, at 10:11 , Don <dlewis6767 at austin.rr.com> wrote:
> >
> > Thank you, Pete.   -Don
> >
> > ==========================
> >
> >
> >
> >
> > On Sat, 2017-12-09 at 05:57 -0800, Pete Lancashire wrote:
> >> Here's a look at a 723-C (1,000 cps) and how its power supply cap was
> >> handled and a good look inside
> >>
> >> https://www.eevblog.com/forum/reviews/vintage-teardown-general-radio-
> >> 723-c-vacuum-tube-tuning-fork/
> >>
> >>
> >> The GR Experimenter
> >>
> >> http://www.americanradiohistory.com/Archive-General-Radio/GR%20Exp%20
> >> 1941_10.pdf
> >>
> >> There is another Experimenter that goes into how the tuningfork was
> >> made
> >> but can't find it
> >>
> >> -pete
> >>
> >> On Sat, Dec 9, 2017 at 5:18 AM, Don <dlewis6767 at austin.rr.com> wrote:
> >>
> >>>
> >>>>
> >>>> I was fortunate to find a vintage, General Radio (GR) Model 723D
> >>>> Precision Oscillator (tuning fork).
> >>>>
> >>>> The exceptional wooden case is as 'exciting' to look at as is the
> >>>> mechanical tuning fork inside (400Hz).
> >>>>
> >>>> As it is ac powered, I'll need to recap it before I turn it on.
> >>>>  Then, we can test for accuracy! (sic).
> >>>>
> >>>> A real class-act, 'time-nut' oscillator from the last century,
> >>>> predating crystals.
> >>>>
> >>>> Don
> >>>>
> >>>> Don Lewis
> _______________________________________________
> 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.
>