Here is the link to some fine pictures and the schematic. Its uasable. http://worldpowersystems.com/J/instruments/GR723/ As a heads up the AC power comes in and is immediately doubled. Loaded something like 164 VDC. Reg tubes 107 V. Osc draws 35 Ma at 135V B+. Fil 1.42V@47 ma. Distortions quite low .219% Tek AA501. IMD 5.59% Tek AA501. I actually used independent supplies when I fired it up the first time. Totally did not trust the power supply. Takes about 20 seconds to start up. You will hear it running quite apparent. I have a theory. Crystals were invented so you would not need to listen to the tuning fork. Regards Paul WB8TSL
On Sat, Dec 9, 2017 at 11:37 AM, paul swed <[email protected]> wrote: > 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
