Cathode Ray Tubes: invention, explanation and experiments
ฝัง
- เผยแพร่เมื่อ 14 พ.ค. 2024
- We explain how Cathode Ray Tubes (CRTs) were invented and how they work, and hook up a few to light them up. They are as intimidating as they are awesome. But did you know that they led to the discovery of the electron, and the birth of a new field, electronics? And of course the invention of the oscilloscope and modern TV!
Link to Eric's scope clock design info:
github.com/schlae/crt-driver
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00:00 Recap of previous episodes and high voltage warning
01:06 High voltage equipment and CRT basics
02:54 Geissler's discovery of the gas discharge tube
03:32 Crookes' discovery of the Cathode Ray Tube
04:41 J.J. Thomson's CRT explanation, electron discovery
06:22 Braun and Whenelt's development of a practical CRT
08:18 Main electrodes of our T527 tube
09:45 Why the cathode is at -4kV below ground
10:35 Why we need a cathode isolation transformer
11:26 First power on
12:04 Deflection plates
13:46 All the electrodes in a modern tube
15:01 How focusing works
16:30 Hooking up brightness
18:04 Displaying shapes!
19:40 Making an oscilloscope
20:57 Powering up a miniature tube
22:00 Large tube, Eric's CRT clock - วิทยาศาสตร์และเทคโนโลยี
I wish I had this kind of equipment to play around with. I recently acquired 5 mobile data terminals that came out of 80s police cars. They all have 5" amber CRTs in them. Still work!
I used to have one of those. Wish I knew how to write to the internal flash memory.
Can you give me the model? Would love to see these work.
@@unmanaged Motorola MDT9100
@@unmanaged mine are MDT-9031
Do you have SCMODS?
If you adjust the focus bias in the opposite direction (opposite polarity) i.e. making the spot even more defocussed and bigger, eventually a sharp image that resembles a lunar landscape comes into focus. This is image a magnified view of the cathode. Effectively creating an analogue non-rasterised electron microscope.
This effect also exists in optics. A lens between a light source and a screen will have two positions of sharp focus. We are effectively exchanging u and v in the lens equation 1/u + 1/v= 1/f, where u and v are the distances from light source to the lens and the screen to the lens, and f is the focal length.
Oh I did not think of this. That would be a cool experiment to try!
@@CuriousMarc Please make a followup video on this, maybe a short? Pretty pretty please :D
@1:00 - I can assure you - your production looks like an OSHA lab compared to Shango066. I really enjoy both varieties of approaches to high voltage.
In my youth that first moving spot would have counted as entertainment. It brings back memories of the disappearing spot on old TVs when they were switched off. We watched that too.
That came back in the early years of Android phones, where everyone installed that App, when you press the power button for standby, it whipes the screen to a small line that then shrinks to a small dot like the old CRTs did. And I had it too on my very first Android phone, sure enough!
@@hamandwine Have you any memory of what that app was called, as I would like it on my phone. Or.. I could Goober it.
@@hamandwine that was the default behaviour of one of my old Android OSes' graphics. It looked so good - they really need to bring it back!
@@gloverelaxis it really did look fantastic on OLEDs. It’s a shame they removed it.
@@hamandwine I still have that phone in a drawer somewhere. It was my favorite thing about it, was devastated to learn the replacement phone did not have this quirky feature.
12:49 DVD logo! I've had one of these small circular tubes sitting unused for years, this video is great inspiration to get it working.
16:22
Be careful!
“Did Jim say that I didn’t see it I SAW IT!”
The invention of the DVD logo
Thanks for the great history lesson! I also really appreciate you getting the pronounciation of all the non-english names right. It shows the respect for the gigants on whose shoulders we stand.
The worst jolt of my life -- it really could have killed me, was coming in direct contact with a deflection yoke. If someone wasn't there to cut the power I might not have made it. Since then, I've stayed away from CRTs -- at least the back of them
I'm 17 and so far I have yet to be shocked in the three years of being around them. Specifically in the Macintosh plus, I fear for the day I too will be shocked.
@@BottomGear2 My dad was probing around a chassis one hand in a pocket rubber mat etc.. Then the dog walked up behind him on the concrete floor with a wet nose. Not sure who was more surprised :)
@@BottomGear2 Simply respect electricity, both high potential and low potential. Some can shock, some can burn or fry (conductors or expensive electronic parts if not you) and some can do both. As much as possible, avoid touching any circuitry that is not known dead and discharged except in the manner it was designed to be touched. While it's not generally a problem with modern equipment with proper grounding, older electronics could unexpectedly bear a high voltage potential to a ground that you might contact in some other manner, so insulated sole shoes and watching what your other hand might be touching (keeping it behind the back is a good idea) are additional precautions when dealing with equipment that is connected to the line. Electricity is a coiled snake ready to bite you in the suitable circumstances, so don't give it any opportunity to enjoy such an event.
@@1boobtube zap! YIPE!
Deflection yokes hurt really really bad. I feel your pain ;)
Nice video...
I am 74 years old and retired, but in my youth I worked in Tektronix technical service for South America.
Working with CRT's was a regular part of my life. I have worked with all kinds of models and know them very well.
I can say that, although today they are obsolete and oscilloscopes are mainly digital, a good analog tube oscilloscope is invaluable.
Among my memories, I have a small Philips DG7-36 tube, and several microwave triodes. For fun, I'm thinking of building myself a small oscilloscope... Things we retired people do when we have a lot of free time...
What a lucky man, radiofun just made one with the same tube. Here is the link to his channel th-cam.com/users/radiofun232
I'm 72, and I built CRT's for HP in Colo. Springs. I play with longwave radio in my dotage. :)
I'm 27 and I really like analog CRT oscilloscopes (and things), I personally prefer them to the new LCDs. I know that the newer ones have their advantages (I work with them in my work, I'm an electrician), but I prefer CRTs for my "hobby" home use, as they are beautiful and have their own charm. I have several CRT oscilloscopes, a CRT cardioscope, tube CRT televisions from the 50s and several screens at home.
wow, great video. Once a long time ago I made a (basic) osciliscope with an old 20" tv. I kept the old yoke connected to complete the high voltage circuit, then used a similar yoke on the neck of the tube (after sorting out the vertical and horizontal parts of the yoke). Then by aplying an amplified signal to the yoke on the tube, I had hours of fun displaying lisajou patterns on the screen. Audio signals were fascinating too. By varying the volume of the signals so many wondrous patterns could be displayed. Thanks for the tutorial and my trip down memory lane!
My love for CRTs has an incredibly fast refresh rate! This video was incredibly refreshing.
What a treat of a video, fun to see you playing along with these old tubes! Haven't handled a live CRT since mid 90's, so I really enjoyedwatching
This was such a great video. It helps me appreciate _Marco Reps_ comments a lot more when he discusses the equip me covers.
CRTs are unreasonably cool. I particularly love the very last generation of them. FHD 1080i or HD 720P is truly a ludicrous thing to expect of a CRT but those crazy engineers managed to not only make it possible, but even make it relatively inexpensive. There's a thing about CRTs that you just don't get from any other display technology: a sense of depth. Because of the glass and the thickness of the glass between the surface and the phosphor layer you end up getting more of a "window" or "vista" effect than you do from any other panel technology. I love it, because the high-res CRT panels, particularly those from Sony and Samsung, have rich enough colors and deep enough contrast that you really feel like you're looking through a window into another world when you use them. If I could, I would absolutely have one of the old Sony 1080i widescreen CRT televisions for PS2 era emulation. I even have a PC that I've set aside just for such a purpose because the GTX9xx series was the very last one to support the DVI standard with analog RGB signaling. And an old i7 7700K with a GTX960 is a perfect platform to run PS2 and Gamecube emulation on.
I watched a video recently about a 4K CRT monitor somebody had, made by Siemens or Fujitsu IIRC for medical purposes. Monochrome of course, which makes high resolution easy due to not needing shadow masks.
What about CRT computer monitors? Some of them had high enough scan rates to do ridiculous stuff like 1536p at 85hz
@@mr.jamster8414 Yep, and those are also very impressive, though often in smaller screen sizes compared to the 1080i television tubes, since it wasn't deemed as necessary to make a screen that close to you particularly massive. The fact that they maintain a similar tube length allowed them to decrease the deflection angle and meet those high scan rates for resolutions even higher than FHD.
that makes a lot of sense! @@mndlessdrwer
@@mr.jamster8414 If you do find yourself in a position to acquire such a monitor and you have a place to display it, you should definitely consider it. Just make sure it works and isn't washed out or dim. A modest amount of correction can be made by fiddling with the adjustable resistors on the control board to increase the cathode ray gun output, but you can't really do anything about missing phosphors. If it's too dim or there's noticeable burn-in, then it isn't worth consideration. CRT displays are wildly fascinating to me and have a unique image aesthetic that you cannot get from any other kind of modern display, so they're still worth the addition to your tech collection. Even better if it's a monitor that features a VGA or DVI-I input for proper analog RGB signal transmission. It is also easier to find a digital to analog converter board or a cable with the DAC chip built into it if the receiving side is already playing nicely by featuring a connector as ubiquitous as VGA.
Edit to correct the DVI version referenced for analog RGB signal.
Great video as always!
It's nice to hear CRTs history for refreshing knowledge.
Cool setup for running tubes on table! 👍😎
Thanks for the history reminder - always an interesting story...which reminds me! In the mid-70's, my school physics teacher proudly introduced the class to the School's two new, very expensive 'Maltese Cross' CRT's. He proceded to spend much time explaining that they were very delicate and had to be treated with great care. He proceded to demonstrate how not to knock them...by tap, tap, tapping one of them on the bench. Tap, tap, tap CRACK!!!!! Some wise-ass piped up (it may have been me!) that the school now had ONE very expensive Maltese Cross tube!!!
This is our Freemason history, all lies, the technology was already here. We will end up returning to CRT. There were no inventors.
Smokin' oldies! CRTs were awesome, but their time has gone.
As a test tech, I worked at a test bench with a big, heavy Tek 541 scope blowing hundreds of watts of hot air on the bench. My fingers got blisters then callouses from constantly turning the knobs as I was going through the tests. It was a great day to celebrate when the company replaced them with HP 1740 series scopes, which were much easier on the fingers. Now the same capability scope fits into a small fraction of the space.
When I was very young I remember my father was playing around in the back of a tube tv with a screwdriver in his hand and got thrown against the wall and the screwdriver had the flat blade half melted off, I learned a lesson that day, him too.
My Dad worked fir a company back in the day called D:E:R. You used to rent your TV or fridge or even washing machine from them. I can remember him doing private jobs repairing tv’s on the kitchen table and always making sure he discharged the crt once he’d unplugged the trippler. By contrast his step father used to repair vintage valve radios and would work his round the anode caps, touching them with his bare fingers, until he found a dead one. !
It's more likely those weren't anode caps, but grid caps. Unlikely to have dangerous voltages on them, and touching one with a finger would inject some mains hum as a test signal.
Yeah, they were sold to a newer competitor named l'Easy. Then the brand was turned into a money lending company.
This is a channel where, with every new episode, one can sit back with a bag of popcorn to enjoy the consistent top quality technical content. So much fun! Thank you Marc!
5:44 love that radius measurement right there (the same concept we learned in school). Thank you for putting this together.
I LOVE CRTs! Fascinating stuff, indeed. And that clock looks super!
I was talking recently to a fellow engineer how such a pity it is that so much research & the sheer amount of knowledge that has gone into the development & production of CRT related technology & it has all but virtually ended. Some of the CRTs i have in my personal hoard are just phenomenal pieces of art looking at the exquisite amount of stuff that has been done to construct it. I hope that oneday there will be something that calls for the technology to be revisited & i pray that all the incredible experience & knowledge is not lost by then!
If you want to know what electricity can do to you without seeing gore then I highly suggest watching Big Clive's video about people that use microwave transformers to do wood working art and paid the (sometimes the ultimate) price. Be careful out there.
best line: Which eventually led to this channel. Very interesting video as usual.
Fantastic video! Thank you for explain in both historical, but also in electric-electronic way how the CRT is working.
I loved to watch this video, and many questions were answered for me! 🙂
Enjoyed the good explanation and demonstration. An early interest in CRTs lead me into a life long interest and career in electronics.
Thank you very much for telling us the History and the function of a crt. I remember Back in the 90's when i was a kid i asked my Patents how a TV works and None of them could Tell me. So i looked it Up in an encyclopedia and there was a small Text about a Kathode and Anode and a small picture. That was it! Now try to understand that as a kid without any other explanation😅
Thank you for this! It made understanding CRT electronic voltage input much easier for me to understand.
I don't know anything about electronics.
Yet I've seen every single video you posted.
These keep me on the edge of my seat every single time!
Thank you so much!
Super cool stuff! Great job explaining how they work!
The tiny oscilloscope reminds me of my uncle's sweet 70s quadraphonic Marantz tuner.
I loved the story time you made! More of those, please!
I'm amazed at how much technology goes into making the DVD screensaver. It's a wonder of miniaturization that it could all be packed into a tiny box that would sit in your media console.
2:54 Yesssss! I've had a hankering for a good elevator music explanation.
Wow. Arthur pronounced correctly. (And all German names as well.) Impressive.
Also: We teach kids in school, how a CRT works, including the nature of electrons... how far have we come.
Great video! Thanks for the no-nonsense, easy to follow tutorial😊
What an excellent video, had me hooked all the way through!
Let's hear it for the fantastic work of Scientific Glassblowers without whom so much progress could not have been made.
Love this! Takes me back to high school electronics classes!
Using a filtered DC supply for the heater supply may reduce that noise. Great Video!
Totally awesome =D A joy to watch this channel!
Thank you for the history lesson!! Fascinating stuff
Looking forward to the episode where you show the episode on a tube, record that on a modern camera and put it on youtube.
Paging Adrian Black and Paul Carlson!
He's going to make his own slow scan TV for the Apollo ground station ;-)
@@zyeborm Yeah, basically two sawtooth waves for deflection (at exact frequency multiples), then apply the received intensity signal to the modulation grid. So really basic triode amplifiers for the high voltage amplified signals.
That's definitely a unique clock. :) I was never fan of CRT's but this video made up a lot for them. ;)
Awesome! Amazing video. Analog electronics is so fascinating.
Thank you for motivating me to work more on my own CRT project - based on the tiny D3-11GJ (only 500-1000V). I am currently planning to design a proper deflection amplifier & a better (resonat switching) power supply for it.
I've been wanting to fix a 1949 round Admiral CRT and I have a tektronix oscilliscope that doesn't have any deflection. I want to learn to fix them so that I can better support my currently working Philco Predicta Princess 17". I love that thing, so this channel seems like something I'll love too. I kinda want to fix them back to stock and then use the regular inputs to put computers and syntehsizers in. I already do that with my Predicta, I have a raspi and converters so that I can put youtube videos on it. It's a trip watching modern content through a 60 year old TV.
You guys are awesome! I was raised around CRT's and I love 'em too.
They're majestic and elegant... Despite the clumsy envelope 🤣
I really miss them showing up on the side of the road to play with haha... I have a trio from a projection set that are just keeping the air out... want to see them live a new life. Rather versatile I figure, can either drive them full tilt for some projection (still on the lense frame) or pop them out and dial them back for direct view... No worry about burn in for the latter methinks 😁
All observations to safety of course, but I was still happy to see Eric's use of the magic fingers to diagnose the focus. 👍
Great work as always from you all. I was reminiscing while watching this as I used to work fixing rental TV's here in the UK 40 years ago. I found it amusing when you were on about 4KV and being cautious, which of course is more than correct, and thank you for reiterating it to todays audiences, but we used to work on tubes\CRT's\televisions with 24KV on the final anode. Those were the days...
The current supply capability of most of those 24 kilovolt ultor supplies was around 1 mA, which is unlikely to kill but could still shock enough to make one jerk violently, which could lead to other injuries. The CRT aquadag capacitance alone could store up a nasty shock and some glass formulas would even be able to build a charge back up after one discharged it. I ended up taping foil to the 'dag and using a clip lead from the anode button to the foil to ensure it was kept discharged.
@@SeekingTheLoveThatGodMeans7648 You are happy to say that it was unlikely to kill. While that may have been the case please explain to my late work colleagues family. The inside of a TV cabinet was often a sharp and dangerous place, especially with chassis built the way they were. One shock could and did rip the wrist open , thus enabling a painful death. Might I suggest that while you appear to have knowledge of CRT's, and yes we always discharged them before touching them because they did manage to store up their own charge, you have not worked in a high voltage environment and are in fact sprouting what you think is important to you. If you had worked in such an environment, then you would have known, and therefore not commented in such a glib fashion. You may reply and apologise or just stay quiet. This reply is posted In memory of my old work friend. p.s. This is available to be read by everyone else therefore, think about how you wish to be seen as an evidently religious person with a name like yours.
@@stephendavies923 Deary me, what a completely unwarranted, sanctimonious lecture. Well, I did work in that environment, and he's absolutely right in what he said, the shock from a TV anode causes a violent jerk response which could lead to other injuries. Why you took it on yourself to take such offence to that is a mystery. He's got nothing to apologise for, get over yourself.
24kv is getting into the pretty hard X-ray level isn't it?
@@zyeborm yeah, but X-ray warning sticker felt long time ago, making the tube safe for operation.
CRT Envy! That last thing, so cool.
Another great one Marc... Got a trio (RGB) set from a projection TV I'm about to fire up and can't find much on them... Not quite the same because of the magnetic deflection but this is useful to have handy for GP reference
Great video, Marc!
That was super fun, entertaining and educational! Thank you! :)
I have a cool scope that projects onto a curved surface to make it more compact, I'd love to figure out how to get it running. This video helps a bit, but still need to do some more searching
Funny you make this video at this moment in time. I've been playing with an old P7 phosphor radar tube lately. I wound my own flyback transformer using a 3D printed spool and and the recycled core from another shorted flyback transformer. It powers everything including the 6.3V heater. I'm now working on a linear amp to drive the steering coils but I'm not having much luck. It needs to swing +-25v in my case and I'm having bad luck picking the wrong transistors from the start and having all sorts of weird problems. Good luck on yours!
I just bought a studio apartment and it comes with an old CRT TV included, I'm going to have a lot of fun with it! 😆
If you can get a hold of any old military aircraft displays theyre often CRT and can be pretty cool because of the history and application. Radar/B-Scope displays, or Radar Warning Reciever displays come to mind.
Wonderful video and great explanation of how CRTs work! Can you make a "part 2" video explaining how vidicon tubes/cameras work?
A new Curious Marc never fails to brighten my day. In this case in nice shades of green with accelerated electrons smashing into phosphors, with perhaps a hint of X-rays for flavor..
Last time I messed around with a CRT bench lash up I popped the ~1.25V filament when a bias line shorted to it, but at least I was able to get it biased well enough to show a decent spot before the incident. Was a cheap and even now pretty common camcorder viewfinder tube I picked up for next to nothing but still a bummer because I wanted to play with the magnetic deflection.
I've been collecting CRTs and equipment containing CRTs for a while; my current favourite is the CRT from a 1950s Ekco aircraft radar with an orange phosphor.
That’s a whole new level!
Very instructive vidéo, many tanks
and again, 'thumbs up' before watching 😎
Yes, there were times when there was a debate whether it was better to use an analog deflected tube or a tv-like line-by-line deflection as a computer screen ;-)
The analog deflection triggered by an analog x and an analog y signal from a computer could show a calculated polygon on the screen, beeing it text or 2D vector graphics or a computer game. You showed it in the last scene...
The calculated vector coordinates x and y could be directly used (just amplified by the right amount) to plot things on the screen, it just needs to be redrawn ("refreshed") many times per second, otherwise it would flicker too much. So when there is too much detail going on, too many vertices to be drawn, it would flicker too much.
It's a bit like a laser show, except that a laser show uses tiny mirrors as deflection devies, one in the x- and one in the y-direction.
Thanks for this video!
Another excellent demo. Seems vaguely familiar to me for some reason. The transformer near the tube brought back traumatic memories of my own. The transformer needs to heavily shielded or at least three feet from the tube.
Great video!!
Reminds me of trying to get a product to work.... It was a front of class oscilloscope demonstrator based on a 28" amber CRT. As the CRT's were all one off hand made tubes each product needed considerble hand tweaking.
The explanation of focusing was excellent. At my old job, I talked to an electron microscopist (is that a real word?) who explained focusing to me and I sorta just about barely understood. Finally, watching this, I get it... must be the elevator music! ;)
I was fascinated by lissajous figures when we were shown them at school.
Old valve tv deflection yokes had a massive voltage across them. The waveform was a spike, a few kv, but thankfully only about 8 microseconds wide. It was wider with the old 405 but not so high. Still a hefty jolt, though.
Amazing how simple the CRT was, and how advanced it became, before finally being outmoded by LCD and OLED. I used to repair Apple, Viewsonic, Trinitron, and other common PC monitors made from the 80s to mid 00s. It was also amazing how quickly PC CRTs went extinct, almost overnight! I still have my degaussing coil, discharger, and other tools, but I doubt I'll ever need them again. All the great modern CRTs, and beautiful vintage ones, are all gone or in the hands of collectors. The last CRTs I touched were total junk, whole-unit swaps out of Apple eMac (educational models).
I used to work with RGB video projectors. The tubes were set up like the clock, but went through filters and lenses to project a color image. They had to be aligned using many electronic controls. Interestingly, the phosphors were different in each tube, producing the optimal color to be filtered.
Some of those CRT projector systems are extremely impressive, even by today's standards. I think some of the very highest end could scan up to 150-160KHz?
@@startedtech I'm guessing that's the H frequency, corresponding to 1200 lines at around 100 Hz V ?
If you get some of the glare filter material used on computer displays - the fine black fabric like stuff - and put it over the burnt in tube it greatly improves their appearance, both operating and not!
Very cool stuff!
This is so cool, like a magician sharing their secrets.
So Cool. I love CRT stuff
On those occasions where someone is close to high voltage, standing behind and popping a bubble-wrap bubble is usually good value :)
amazing how it all works.
dudee the color coding was great!
YOU are guys are amazing!🤟👍
excellent video!
Those pretty scope tubes look nice, and of course the Apple IIgs in my basement looks great on its original monitor, but I definitely am intimidated by them (and not just the high pitched whine of a flyback transformer). Somewhat anxious about the fact I have a Mac Classic I want to open, inspect, maybe revive if it doesn't have too much battery damage, but there's a big ol crt that will be staring me in the face... Also want to fix my (nothing too special but it's mine, etc) analog Tek scope which failed while in very safe storage in my office...
I can attest to the susceptibility of CRTs to stray magnetic fields. For a while I had a monitor sitting on top of a homebrew computer. The raster always had a slight wavering to it that I couldn't find the reason for, until one day I happened to run it with the monitor sitting to one side on the table, and the wavering disappeared. That's when I realised it was due to the magnetic field from the largeish power transformer inside the computer.
I wish there was a super like button. Great video!
I have a similar small CRT shown in this episode, and always wanted to try my hand at making something with it. Mr TubeTime has a perfect example of it! Show off :D
LCDs may be more convenient, Oled may have better color reproduction, but damn! CRTs are just way cooler than anything else. I've repaired many CRT chassis, mainly as an arcade tech, and there is something so rewarding about calibrating geometry, color, and convergence that feels so rewarding. Next up for myself is finding a way to matrix a signal out to my CRT video wall. I've never done much work with oscilloscope tubes, cause all my old oscilloscopes have never needed repairing! I still prefer analog scopes for when all the fancy hold and logic analyzing functions aren't necessary. The snappiness of the controls and display of old tube scopes is a joy.
Du hast dich selbst übertroffen in this video, thoroughly entertaining and éducatif à parts égales. Muchas gracias Marc 🍹
And that is barely scratched at the surface of advanced crts.
Distributed deflection, micro channel plates, multimode Storage, scan converters and on and on.
Nice shout-out... the "Tube" in TH-cam is the one JJ Thomson invented just over 100 years ago :)
Very close to having a game of pong there!
Looks like someone is still playing with CRTs. A least I'm not alone
Nice CRTs - I've got a few of these lying around and it makes me wonder if I could get them going with a flyback transformer turned down to "just" a few kilovolts, but dividing and measuring the voltage would be a pain in the ass. Separate supplies give you the possibility to get exactly the voltages you need.
Yes, old flyback supply and resistor dividers would be tge most common way to do this.
I have a NOS Heathkit CRT in my collection that I need to do something with.
Marc using the word 'doo-hickey' and doing the hoorah thing is why I'm here. ;)
Working on colour monitors and displays always concentrated the mind. 25kV of EHT……
You should really do a companion video for this covering camera tubes given they are so very similar in many ways.
Soon to make my own hv supplies
Neat stuff!!!
What wavelength of UV did you use to fluoresce the front of those CRTs?