[HN Gopher] The vacuum tube's forgotten rival ___________________________________________________________________ The vacuum tube's forgotten rival Author : bangonkeyboard Score : 151 points Date : 2022-03-27 15:41 UTC (7 hours ago) (HTM) web link (spectrum.ieee.org) (TXT) w3m dump (spectrum.ieee.org) | hilbert42 wrote: | Magnetic amplifiers have been in use long past WWII, they were | never obsoleted by War's end. | | For example, many stage lighting systems still use them. For | example, the Sydney Opera House which opened in 1973 with the | latest equipment used them for its stage lighting dimming | (although they have now been replaced with solid state dimmers). | | Magnetic amplifiers are wonderful devices albeit a bit slow for | some applications. Moreover, unlike SCR and other solid state | switching, they produce no RF switching noise. | krallja wrote: | > In the 1920s, improvements in vacuum tubes made this | combination of Alexanderson alternator and magnetic amplifier | obsolete. This left the magnetic amplifier to play only minor | roles, such as for light dimmers in theaters. | c3534l wrote: | RTFA | Lammy wrote: | "After the war, U.S. intelligence officers scoured Germany for | useful scientific and technical information. Four hundred experts | sifted through billions of pages of documents and shipped 3.5 | million microfilmed pages back to the United States, along with | almost 200 tonnes of German industrial equipment." | | Don't forget "and a bunch of actual Nazi scientists just for good | measure" | https://en.wikipedia.org/wiki/Operation_Paperclip#Key_recrui... | ililic wrote: | What is "alt-tech" ?? | | Is this a term used commonly? It's referenced in the subtitle but | no where in the article. | ILMostro7 wrote: | Presumably refers to technology that was supplanted by an | alternative technology or implementation for wider use. | Inferred meaning, no sources to cite. | noipv4 wrote: | I remember seeing mag amps in the computer PSU, back in early | 2000s, before solid state regulators took over. | krallja wrote: | > In the mid-1990s, the ATX standard for personal computers | required a carefully regulated 3.3-volt power supply. It turned | out that magnetic amplifiers were an inexpensive yet efficient | way to control this voltage, making the mag amp a key part of | most PC power supplies. | 8bitsrule wrote: | Thanks! I'd long wondered exactly how radio carriers were | modulated before vacuum tubes. (Technical details of that era are | often skimpy in histories.) | | This chronology of AM radio is interesting: | [https://web.archive.org/web/20071118155548/http://members.ao...] | It mentions Fessenden's 1906 Xmas broadcast, and it looks like | he'd just gotten one of Alexanderson's alternators. | | Paul Mali, _Magnetic Amplifiers_ (1960;PDF) | [https://web.archive.org/web/20061114175548/http://www.pmille...] | | Home-made MA's: [http://sparkbangbuzz.com/mag-amp/mag-amp.htm] | myself248 wrote: | You can hear an Alexanderson live on the air, twice a year! | | https://alexander.n.se/en/the-radio-station-saq-grimeton/saq... | | Might want to get a head start on the receiving hardware, | though. Most SDRs don't go that low, and though soundcards can | go that high, their input impedance may not be well suited to | whatever antenna you can cobble up. Oh, and you'll want an | absolutely enormous antenna. Get a roll of cheap fence wire and | string it halfway down the block... | zw123456 wrote: | This reminded me very much of the old mag core memory from early | days of computers https://en.wikipedia.org/wiki/Magnetic- | core_memory | WalterBright wrote: | I saw some core memory cards in the surplus store in the 70's. | Wish I'd bought one just for fun. | nand4011 wrote: | My favorite anecdote about magnetic core memory comes from the | development of the Naval Tactical Data System. | | https://ethw.org/First-Hand:The_Naval_Tactical_Data_System_i... | | A paper bag of magnetic cores disappeared while the engineers | were out to lunch: | | > _But shortly after, the engineer called and asked if the | shipment was there. This did not sound too good. With a little | detective work we found a cleaning crew had worked in the | office while we were gone. A little more sleuthing revealed | that the bag had been accidentally knocked into a waste basket, | and that load of waste had already been dumped into the plant | incinerator. The incinerator ashes were spread over a concrete | floor, and sure enough there were small magnetic cores, about | one sixteenth of an inch in outside diameter, mixed in with the | ashes. The CP-642 B had 32,768 30-bit words in its memory, | meaning, with spares, there were just about one million | magnetic cores in the ashes. At ten cents per core, the ashes | held about one hundred thousand dollars worth of cores._ | | _We reasoned the cores were the result of a firing process, | and the heat of the incinerator probably had not hurt them. | Maybe it even made them better. A quick test of some of the | cores picked from the ashes revealed the cores were as good as | ever. We and a contingent of Univac engineers & technicians | spent a fun filled day rescuing the cores from the ashes with | long needles. The cores were strung into the machine's memory | planes, and it passed all performance and environmental tests | with flying colors._ | | That entire history is worth a read if you are interested in | computer history of the military variety. | kens wrote: | Interesting story. By the way, the NTDS computer system you | mentioned was very successful and important for military | computing, but it's almost forgotten now. | | Wikipedia has more info: | https://en.wikipedia.org/wiki/Naval_Tactical_Data_System | | The book _When Computers Went to Sea: The Digitization of the | United States Navy_ has a very detailed history. | jrapdx3 wrote: | Thanks for that charming bit of history. Humorous but also | astonishing that the cores were salvageable after such rude | treatment. The use of such cores was before my time in the | computer world so I have no experience with them. I wondered | if the tiny cores could have been scooped out of the ashes by | a magnet. I'm sure the engineers would have thought of it, | I'm guessing that would have damaged them. (Or more likely it | wasn't even possible to collect them that way...) | | Threading the burnt cores onto needles would definitely not | be my idea of fun. Though I imagine a needle full of them | would resemble a string of beads. Come to think of it, as | described those cores would make a mighty interesting | necklace (and FWIW my wife thought so too). | krallja wrote: | > Researchers soon constructed what was called core memory from | dense grids of magnetic cores. And these technologists soon | switched from using wound-metal cores to cores made from | ferrite, a ceramic material containing iron oxide. By the | mid-1960s, ferrite cores were stamped out by the billions as | manufacturing costs dropped to a fraction of a cent per core. | erdos4d wrote: | I wonder how a Les Paul sounds through one. | myself248 wrote: | Forgotten? Every military vet I know who worked on electronics in | any capacity, raves about the reliability and durability of mag- | amps. | dr_hooo wrote: | I for instance don't know any vets, so I learned something new | from the post. So I'd say the title is fine. | throwaway73838 wrote: | No mention of musical applications. I'd be curious to hear what | one sounded like. | erosenbe0 wrote: | Another gem by Ken Shirriff! Master of deep-dives into | semiconductor history. | skeptikal wrote: | No forgotten, but definitely hard to get info from. You can find | some books on the internet archive. | | Subs use them, high T and rad places still use them (Im told). | nobodyandproud wrote: | > "Many engineers are under the impression that the Germans | invented the magnetic amplifier; actually it is an American | invention. The Germans simply took our comparatively crude | device, improved the efficiency and response time, reduced weight | and bulk, broadened its field of application, and handed it back | to us." | | Quoting a quote: I found this quote of the 1951 US manual | amusing. | noja wrote: | "Many people forget that we invented the wheel. They simply | changed the shape from square to circle, and changed the | material from volcanic rock." | WalterBright wrote: | My improvement on the square wheel was the triangular wheel. | It had one less bump. | jsnodlin wrote: | TedDoesntTalk wrote: | It's funny today. But to put it in context, many Americans | wouldn't use German products after the war. My parents | refused to buy German cars and other items for decades. | | Much like Russian products are abhorred in America right now. | Caviar, LukOil, Kaspersky AntiVirus, etc... | mirceal wrote: | to be fair: german products are high quality when russian | ones are of questionable quality | TedDoesntTalk wrote: | Some are questionable, yes. But what about food, vodka, | and gasoline, natural gas, and oil? | | I don't think people avoided these products before the | Ukraine invasion. | beeforpork wrote: | > ... russian ... questionable quality | | Caviar is the best in the world! :-) | denton-scratch wrote: | But incredibly expensive. Really, it's just for showing | off. Beluga sturgeons can't be farmed, so they are | endangered. Farmed Italian sevruga caviar is good enough | for a couple of blinis. I'd say it's still ridiculously | expensive stuff, but it's a small fraction of the price | of Russian beluga caviar. | WalterBright wrote: | Which is kinda silly, as all modern jet turbines are | descended from Ohain's axial flow engine which powered the | Me-262 jet fighter. | | The Whittle engine was a radial flow design, which was | bulkier and less efficient, and was abandoned after the | war. | TedDoesntTalk wrote: | I didn't say it was rational. Emotional choices rarely | are. But it made them feel better, and there is some | value in that. | [deleted] | neilv wrote: | > _One Navy training manual of 1951 explained magnetic amplifiers | in detail -- although with a defensive attitude about their | history: "Many engineers are under the impression that the | Germans invented the magnetic amplifier; actually it is an | American invention. The Germans simply took our comparatively | crude device, improved the efficiency and response time, reduced | weight and bulk, broadened its field of application, and handed | it back to us."_ | | Does that sound "defensive" to everyone? | | I don't know this area of engineering, so, to my ear, this could | also plausibly be an almost admiring acknowledgement of someone | else succeeding where you'd failed, combined (non-defensively) | with confidence, because you had the strength or other superior | merit to take it from them? | ILMostro7 wrote: | Not that it should matter, but considering the source (and | time), the phrasing could be understood to imply a level of | pride that we got there first. Although, they do seem to give | the Germans credit for expanding the technology. Nevertheless, | it's the reader that chooses how to interpret the text, and | what lessons to learn from it. | neilv wrote: | That sounds plausible, too. | | Various nationalism and other thinking, in different groups, | at different times, are still largely a mystery to me. It | seems relevant to group thinking we see today, which is still | confusing (e.g., why is much of the thinking and dialogue | around the two main US political parties doing what it's | doing, and how is that representative/determining of what the | broader population actually thinks). | ILMostro7 wrote: | Divide and conquer approach of the populace, IMHO. From an | international perspective, though, it may be useful to spur | competition. | 13of40 wrote: | When I read the title, my first thought was about the cryotron: | "Tantalum in superconducting state can carry large amount of | current as compared to its normal state. Now when current is | passed through the niobium coil (wrapped around tantalum) it | produces a magnetic field, which in turn reduces (kills) the | superconductivity of the tantalum wire and hence reduces the | amount of the current that can flow through the tantalum wire. | Hence one can control the amount of the current that can flow in | the straight wire with the help of small current in the coiled | wire." | | https://en.wikipedia.org/wiki/Cryotron | klyrs wrote: | As far as I can understand superconductivity, the devices are | similar but opposite. Superconductors have a both a critical | current (in the absence of a field), and a critical magnetic | field (in the absence of a current). So, cranking the control | line raises the field, which squelches current capacity to zero | (and/or since there's an excess of either/both, | superconductivity is lost). | kens wrote: | I actually mentioned the Cryotron in the original draft of this | article, but there wasn't room for it. Some of the other | forgotten computing technologies of the 1960s are tunnel | diodes, microwave oscillators (Parametron), and | electroluminescent photoconductors. | stevespang wrote: | IndrekR wrote: | Did a design with a tunnel diode in 2011. Around 300 devices | were made and sourcing the diodes was not easy -- but still | possible. | tmountain wrote: | Article seems to be behind a paywall. | mtreis86 wrote: | If you close the popup window asking you to make an account the | article is still there in full. | sreevisakh wrote: | That can't be. Spectrum articles usually aren't. I was able to | read it in full by selecting 'Keep reading'. | agumonkey wrote: | just in case, someone posted the wbm link | http://web.archive.org/web/20220327154828/https://spectrum.i... | zmix wrote: | I could access the article fully from Germany. | neonate wrote: | http://web.archive.org/web/20220327154828/https://spectrum.i... | jmbwell wrote: | And to this day, the representation of memory contents at the | time of a kernel panic is called a "core dump." | nateburke wrote: | Doesn't a form of mag amp figure prominently in Gravity's | Rainbow? | | https://niklasriewald.com/2020/01/02/the-math-behind-gravity... | JKCalhoun wrote: | No surprise ... Pynchon writing cyber-punk before cyber-punk. | | Solid-state-punk. ___________________________________________________________________ (page generated 2022-03-27 23:00 UTC)