Continuously Refreshing Television
January 22, 2018 9:34 PM   Subscribe

How a TV Works in Slow Motion (SLYT; epilepsy warning) (h/t)
posted by Gyan (18 comments total) 23 users marked this as a favorite
 
When my dad became ill and couldn't work anymore he started fixing TVs and VCRs in the garage/workshop. This was when TVs were made of wood and had the circuit diagram printed on the inside. He showed me how an oscilloscope worked, deflecting the beam with magnets, showing the relationship between a guitar string and what you see on the screen. I could see radio waves, and have a sense how it worked.

Then he showed me how to tune it to pick up TV signals. I UNDERSTOOD. It was such a revelation! My dad had a master's degree in electrical engineering and he totally made an artform of 'explain like I'm 5yo'.

As a pre-teen I knew about the cathode and the electron beam, the yoke and the vacuum tube coated with phosphur. Not in great detail, but enough to not shrug and presume it runs by some magic only adults know about.
posted by adept256 at 10:48 PM on January 22 [17 favorites]


Whoa. Maybe add a migraine and/or nausea warning.
posted by Thella at 1:45 AM on January 23


Very cool, and much better than the dude-bro 'Yo check this cool-ass mofo super slow camera we totally scored!' Interesting and informative and worth the ten minutes+
posted by From Bklyn at 2:26 AM on January 23 [1 favorite]


This brought back a lot of memories of me as a kid putting my face right up against my parent's TV to look at the little red, green and blue rectangles.
posted by AlonzoMosleyFBI at 4:25 AM on January 23 [2 favorites]


I do feel vaguely cheated that all the knowledge I have about analogue video systems - I had a holiday/weekend job fixing TVs and radios in a backstreet repair shop when I was at school, yay ubernerdity - is now effectively obsolete. A chain of development going back to Blumlein and Farnsworth terminated by those darn digits.

Pixel-addressable digital displays are all very well, and the science and technology of creating huge areas of active, transparent electronics with micron resolution is marvellous in its own right, but it lacks the sheer chutzpah of having an actual particle accelerator on your desk aimed directly at your eyes, and commanding the electrons to dance, baby, dance, in that wonderful line/frame choreography by brute force of primal magnetism as they hurtle to their doom through vacuum before smashing into carefully formulated phosphors and giving up their energy in photonic conversion. Something we first learned to do, and get into actual homes, in the 1930s.

All gone, like tears in the rain - if tears were fundamental particles and the rain was the rain of electromagnetic wave packets.
posted by Devonian at 6:25 AM on January 23 [16 favorites]


Whoa, I've never really thought about scanlines before in a concrete way. Like, I know that when you're programming an Atari 2600, you've only got x number of scanlines' worth of time to do computation before you have to start drawing the screen again (line-by-line!), but I never really thought about how short that time is and how it relates to a the physical movement of the beam. Super cool.

Also now I want an OLED TV. I have a 10-year-old 720p plasma that I've never replaced because a) it works; and b) washed-out LCD blacks make me sad. So it's nice to know that there's a nice-blacks option on the horizon once this TV kicks it (but hopefully not any time soon).
posted by uncleozzy at 6:44 AM on January 23


That was very informative and I too want an OLED tv. I'm still rocking an old 1080p Sony CRT that weighs a million tons.
posted by mmascolino at 8:11 AM on January 23


A few years ago I was in Paris so I visited the Musée des Arts et Métiers, which at the time had an exhibit about early television. My dad was an electrical engineer and I'd grown up nerdy, so I'd known how CRTs worked for most of my life, but I was totally astonished to learn that before that there was a mechanical system that used spinning discs with holes in them to serialize the two dimensional video into a signal that could be broadcast, transmitted, or (and it sounds like this was fiddly and expensive and they didn't do this much) recorded.

It's pretty clever. Now that I'm thinking about it again, I'm wondering how hard it would be to just make my own - it doesn't seem like it requires any particularly tricky or manufacturing. HMMMM!!!
posted by aubilenon at 8:41 AM on January 23


Now I kinda want to dig up a macro lens and aim it at the same piece of paper on my wall that my projector covers. I’ll probably just see blurs since I don’t have the projector perfectly focused.
posted by egypturnash at 9:17 AM on January 23


aubilenon - if you google 'build mechanical tv', you'll find various resources to help you in this. It's quite easy to get something going, but quite hard to do with any semblance of impressive results.

When the BBC was investigating TV transmissions, it ran Baird's mechanical TV system alternately with the Marconi-EMI electronic system during a test period in 1935. In hindsight, choosing the all-electronic system (which subsequently continued in use until the mid 80s) was obvious, but at the time there was a lot of politics and controversy involved alongside the business of getting brant-new technology on the air.

(Bonus feature: a recreation of the first-ever TV drama, The Man With The Flower In His Mouth, transmitted on the Baird system in 1930.)
posted by Devonian at 9:51 AM on January 23


When I watched this, I was instantly transported to my Nana's house where I'd, as a preschooler, sit with my face inches from her wood-paneled TV trying to figure out how all of those tiny red green and blue dots somehow turned into Mr Rogers.

I swear I could even smell that staticky smell that old TV's had.

Anyway, for the first time in my dang life I think I understand! THIS IS SO AWESOME THANK YOU.
posted by capnsue at 11:05 AM on January 23


What blows my mind about analog television broadcast and display is that it completely lacked something that we take for granted in the modern age: buffers. There are no buffers, no delays, no sliding window, and no slack. So that tiny dot flickering across your screen 15,000 times per second is in perfect synchronization with the tiny dot on every TV in every home in your town, all of them glowing with the same intensity for the same microsecond.
posted by rlk at 11:22 AM on January 23 [5 favorites]


perfect synchronization

Not quite... if you're 50 miles further away from the transmitter than your friend, then you see things around 100 microseconds later. Can't escape the Great Cosmic Buffer of spacetime. That is mind-blowing in its own way: when you press transmit on your ham radio moonbounce system and hear your own signal come back after 2.6 seconds , I swear you can just catch Einstein chortling in the background.

But yes, inasmuch as anything can be synchronous in this universe, the few million dancing electron dots in the footprint of a powerful analogue TV transmitter - many more, in the glory days of analogue satellite - are pretty much as close as we can get. It is wonderful and perspective-shaking, and again I get goosebumps knowing that we learned how to do this some eighty years ago. We slammed into the buffers of the geometry of the universe, not in some lab, not needing the orbiting atomic clocks and heavy maths of the like of GPS, but in the corners of our living rooms and using nothing more than glowing metal in glass bottles.
posted by Devonian at 12:32 PM on January 23 [3 favorites]


The invention of the original 1941 NTSC* raster scan system, with its sync and blanking signals neatly embedded in with the video signal was quite a feat, but the fact that they were able to add color 12 years later in an entirely backwards-compatible way by superimposing a high-frequency carrier on top and then phase *and* amplitude modulating it, well that blows my mind.
I'm convinced we were more ingenious back then. We invented stuff. Now we just manipulate numbers.

*(Yes, the other standards were similarly ingenious and in some ways better)
posted by rocket88 at 3:46 PM on January 23 [2 favorites]


This has nothing to do with TVs, but this post has reminded me of the old vintage Hi-Fi unit in the family living room when I was a kid (mid-60's). It was a full wood cabinet with a tuner and turntable inside. At the bottom, under the big speaker, was a small power indicator light, covered by a faceted green lens. I used to get down on the floor on my stomach and get my eye right up to the light and look in - it was like peering into a vast emerald cavern. I've never forgotten that.
posted by davebush at 3:51 PM on January 23 [1 favorite]


For the very serious or exceptionally curious, here is a PDF of a 1943 report on Television Standards and Practice - "Selected Papers from the Proceedings of The National Television System Committee and Its Panels". It's over 400 pages long, and includes what is most probably the definitive list of known standards considered at the time the NTSC decided on the 525-line US system.

(These include the long-forgotten British Scophony system, which was quite something. Per Wikipedia: "In 1938, the Scophony company demonstrated three types of 405 line mechanical television receivers at the Radiolympia exhibition in London: a home receiver, with a picture area of approximately 24" x 22" and two systems intended for theater operation, one producing a 6 ft x 5 ft image and the other a 9 ft x 12 ft image". The war killed it off, at the same time as it accelerated radar and radio developments to give post-war TV a much improved set of technologies to draw on.)

So, if you ever wondered how much engineering went into all that - this is the tip of the iceberg, and a very substantial tip too. Although it precedes colour by a decade or more, that's absolutely on the roadmap and its eventual adoption is seen both as inevitable and worth considering in terms of future compatibility.

(It's also enjoyable for the period English - "In the same year, 1936, Commander Craven set forth the necessity for making allocations in the ether spectrum for television stations." - which is sadly lacking in today's standardisation reports. Those allocations, however, were just as mired in politics as today's, with Edwin Armstrong's FM radio network being booted out of Band I after considerable machinations by RCA. The sort of efforts which aren't documented in fancy prose and measured discussion...)
posted by Devonian at 5:02 PM on January 23 [1 favorite]


I teach a Broadcast Technology course at a local Technical Institute and serendipitously I deliver a lecture tomorrow on the subject of display technologies. I'm scrambling right now to modify my lecture to include this video. Thanks Gyan!
posted by Zedcaster at 5:22 PM on January 23 [1 favorite]


Thanks, LG. I guess OLED is the way I'll go when my DLP finally gives up. It also has rich blacks, because the tiny mirrors are facing off into some other direction if they're not making a bright spot on the screen.

I love DLP, by the way.. It's a Rube Goldberg machine. It's the kind of television you would expect from a society that somehow mastered micro-mechanics before truly mastering electromagnetism. It's absurd. A lightbulb.. shines on a grid of tiny mirrors, one mirror per pixel, and those mirrors reflect the light path through a spinning color wheel, through some lenses to a big parabolic mirror and onto a screen. It draws the whole scene all at once, in six different colors, as the color wheel spins.

But, I won't really be delighted until my pixels can be expressed in a particular wavelength in nanometers, instead of some weak blackbody gamut. laser tv or bust!
posted by Xyanthilous P. Harrierstick at 7:12 PM on January 23 [1 favorite]


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