Re: Variable AC supply


Chiming in on ad-hoc variable AC supplies.

We were building an automated mastering console that used 8080 processors. Development was done on an IMSAI 8080 computer and we needed a printer to printout the assembly language source code. All we had was an ASR 33 tele-type that refused to print properly. In abject frustration I hooked up a Tektronix 465 scope (Notice how I’m keeping this on topic.) and looked at the letter ‘A’ coming from the computer and the letter ‘A’ coming from the tele-type. It was then I noticed a 20% difference in the overall timing of the character. I pulled off the cover and in big letters on the tele-type motor was 50Hz. I went to the shop and got a Crown DC300 amplifier, transformer, and an HP 3310A function generator that I set to 50 Hz. Everything now worked. My memory is good because I took a picture of this screwball setup.


On Feb 21, 2019, at 9:36 AM, Roy Morgan <k1lky68@...> wrote:

During a much earlier era at NBS, the National Bureau of Standards, when they were located “downtown” in Washington DC, a standard frequency was distributed throughout the buildings to labs which might need it. I think it was one kc, and I assume it travelled over telephone circuits around the campus. I know nothing about the source of the “tone” but the amplifier involved used the legendary Western Electric 300B vacuum tube triodes. I suspect a General Radio standard frequency oscillator was used. The fellow involved in keeping that running was Bob Balcom, SK lo these many years now. (His callsign escapes me.)

Wishing he had that amplifier now.

On Feb 21, 2019, at 7:31 AM, EB4APL <eb4apl@...> wrote:

During the Apollo era, NASA's Manned Space Flight Network tracking
stations used a COTS Marantz audio amplifier ... to power all electrical wall clocks in the
facility. The amplifier was driven by a 60 Hz signal from the Precision
Frequency & Timing subsystem.
Roy Morgan
K1LKY since 1958

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