all AC vacuum tube circuits? - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: June 17, 2018, 06:34:03 pm
content: Did they have vacuum tube circuits that run like triacs, diacs, etc on all AC without filter caps to make high voltage rails? It's hard to imagine it working.

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2018, 06:56:17 pm
content: Thyratronshttps://en.wikipedia.org/wiki/Thyratron

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 17, 2018, 06:57:20 pm
content: The common microwave oven is one example. (The capacitor is for voltage doubling, not filtering.)

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2018, 07:00:49 pm
content: Quote from: CopperCone on June 17, 2018, 06:34:03 pmEDIT: Triodes, Pentodes etc will also work happily on AC (all hot cathode tubes are capable of rectifying, within limits).

author: CopperCone
author_rank: Super Contributor
timestamp: June 17, 2018, 07:25:39 pm
content: did they have things like dimmers/crude drives that used that kind of stuff?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 17, 2018, 07:49:32 pm
content: Monarch 10EE Lathe for example,http://www.lathes.co.uk/monarch/page2.htmlin 1949, in line with new developments in electronics, the Reliance rotating motor-generator set (DC) arrangement was replaced by a system that used electronic-tube controlled thyratrons to rectify AC current to a variable DC voltage to drive a DC motor.A lamp dimmer made for 5HP DC motors surely fits the bill.Tim

author: Ian.M
author_rank: Super Contributor
timestamp: June 17, 2018, 08:00:09 pm
content: Also seehttps://en.wikipedia.org/wiki/Ignitron

author: floobydust
author_rank: Super Contributor
timestamp: June 17, 2018, 08:15:25 pm
content: Colour organs using thyratrons,that fueled psychedelic rock before hippies could afford SCR's.

author: Benta
author_rank: Super Contributor
timestamp: June 17, 2018, 08:45:18 pm
content: Quote from: CopperCone on June 17, 2018, 07:25:39 pmI can assure you that there isnothingcrude about the Monarch 10EE thyratron drive.

author: Circlotron
author_rank: Super Contributor
timestamp: June 17, 2018, 10:36:48 pm
content: I read somewhere that some very early Morse code transmitters used on aeroplanes were fed raw AC from a wind driven alternator. If the AC frequency was high enough it would have transmitted a tone, not just steady carrier.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 18, 2018, 12:43:04 am
content: There's a user here with a great mercury-arc rectifier as avatar....Small country sized ones:https://upload.wikimedia.org/wikipedia/commons/4/48/Pole_1_mercury_arc_valves.jpgSo yeah, they work.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2018, 10:32:53 am
content: Quote from: Circlotron on June 17, 2018, 10:36:48 pmThe Alexanderson alternator was the first, high power, CW generator for, what were at the time, high frequencies (~100kHz).Although I don't know how practical that would've been onboard aircraft; maybe not much, but then maybe just fine with a tow line antenna.Tim

author: Circlotron
author_rank: Super Contributor
timestamp: June 18, 2018, 11:00:30 am
content: ^^ Yeah, I meant AC HT fed to a tube type CW transmitter, the wind driven alternator simply for power supply duty. One of those old timey HF alternators airborne would be something else again.

author: Ian.M
author_rank: Super Contributor
timestamp: June 18, 2018, 12:06:54 pm
content: Quote from: T3sl4co1l on June 18, 2018, 10:32:53 amIf its a biplane then a loop antenna would have been fairly easy - run just under the skin of the upper surface of the top wing, then to the bottom wing at the outer strut then back under the skin of the bottom surface if the bottom wing and continuing the same on the other side.A trailing end-fed long-wire antenna isn't going to be particularly effective without a metal fuselage as a counterpoise. Metal skinned airplanes became increasingly common from the mid 1920s onwards, as did amplifying vacuum tubes, so the odds that anyone used a trailing long wire antennae with an airborne Alexanderson alternator other than purely experimentally are quite low - by the time metal skinned planes that could form an effective counterpoise were on the market, the Alexanderson alternator was very much on the way out. Also an Alexanderson alternator is a heavy brute - there's no way of avoiding it at the speed it spins using 1920's materials and metallurgy, so it would have taken up a serious chunk of the payload capacity of early planes.There were WW1 era artillery observer aircraft that had an on-board transmitter and a 150' trailing wire antenna, but they used spark transmitters. A 150' wire is a quarterwave at about 1.6MHz - well above the maximum practical frequency for a small Alexanderson alternator of a few hundred KHz.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2018, 03:53:40 pm
content: That would be an odd juxtaposition; I forgot that the two things (generators and biplanes) were about a decade apart. Close but no cigarTim

author: drussell
author_rank: Super Contributor
timestamp: June 18, 2018, 04:00:14 pm
content: Indeed, it is because ofthyratrontubes that SCRs and TRIACs are types of a class of semiconductors calledthyristors.