[HN Gopher] The vacuum tube's forgotten rival
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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.
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