Homemade Cathode Ray Tube, Transconductance Tube Tester, and other stuff

Made this CRT a while ago but did not get a chance to make a video. This video was too long so I did not include the first experiments with the CRT, I might upload these later if there is interest. I am currently making scales for the tube tester meters so the readings are no longer relative.

[jdflyback]

00:57 : Homemade CRT
9:28 : Blocking oscillator circuit
12:14 : Transconductance Tube Tester
20:50 : Thoughts on making Triodes

[Simplifier]

I'm almost certain this is the first homemade sealed-off hot-cathode CRT on the internet. You beat me to it! I'm curious to see how a properly gettered one would perform; at the very least it would probably be easier to adjust. One thing to consider if you're going to build more of these is picking up a flat sheet of pyrex (available for 3D printer beds), and cutting out discs for the face of the tube. Seems like that would be the easiest way to get a regular/even surface for calibrating the beam. I haven't tried it myself yet, but that's my plan for when I eventually try to make one.

Glad my tungsten preparation procedure worked out; I was hoping I had remembered it correctly and not left out any details, it's been a few years since I did it. I think the only thing I might've missed is on larger tungsten (0.5mm and above, where I used TIG electrodes) I would sand the rods on my lathe so that the sanding grooves were helical rather than axial, to avoid air paths. This isn't practical on fine wire though, and I'm not sure it makes much of a difference anyways.

If you're starting to quantify the characteristics of your tubes, one thing that you might find useful is a book titled "Materials and Techniques for Electron Tubes". There's a link to the PDF on my site in my tetrode article, and on page 277 there's an extremely useful table that shows the relationship between filament current, filament size, emission, and evaporation. The rest of the book is great too, but I found that specific page critical to understanding the operational limits of tungsten filaments. The math is kind of unusual, but the data is all correct once you get the hang of it.

Looking forward to seeing what else you make; I think with some bigger glass and some alignment jigs you'll be able to start getting repeatable results. Any plans to make any all-tube electronics, like a radio or an audio amp? Might be a fun project.

[tuopeeks]

Nicely done, think this is the first homemade CRT I’ve seen with a good enough vacuum for thermionic emission.

[TheGiselaSchumacher]

Absolutely fantastic! The CRT especially caught my eye as just a week and a half ago I made a very similar (though much less effective) one! My anode was just a wire as I had recently gotten my new glass tubing and wanted to make a proof of concept tube. While on the pump, I did get a good enough vacuum that 2400V on the anode didn't cause any glow discharge, and when the filament was heated up, as little as 1200V would make the whole phosphor bulb glow a nice red color (mixed CFL phosphors yield interesting colors). This, however, did not last after sealing off as there was a small leak somewhere and the tube was useless within the hour. I made a better version later with a pinhole anode and a shielded filament, but I hadn't noticed a crack in the anode wire seal before sealing it off. I sealed the leak with a dab of JB kwik (works surprisingly well in simple vacuum setups), and opened the stem up for re-evacuation, but the inrush knocked a bunch of phosphor loose. I didn't notice this at first, and my cheap chinese pump sucked some powder in, damaging its vanes. Needless to say, I never did finish re-evacuating that tube. Luckily now I have a great condition Edward's E2M2 and a fair bit more experience with glass. I do feel I should point out that I use soda lime with either Dumet or titanium feedthroughs. I'm not sure if there's anything I can be of help with, but if you're looking for advice or getting stuck with tube making, I'll do my best to lend a hand! Keep up the great work and I look forward to more of your videos! :D

[DiodeGoneWild]

Try to use an Erlenmeyer flask (conical flask) for the CRT front ;)

[frankowalker]

Wow, I've never seen a home made CRT before. Mega congrats.

I love the rest of your home made equipment too. :)

[nikomaukkonen]

Wow, you're at it again, Awesome work by the way!
I'll add a hot cathode CRT-tube to my list of tubes to be made.

Do you have any tips on how to get an even coating of phosphor on the glass? That would really help me out.

I've accidentaly made a few thyratrons in the process of trying to make triodes. It turns out they're stable enough to be used in relaxation oscillators and i've built a few frequency generators out of them. It would be interesting to see you give it a shot.

[gil]

you sound like a university student perhaps someone taking electronics but from your skills you appear to be someone who has taught electrical engineering and has years of experience . Either way everything is amazing, home made vacuum tubes and a that clock or a CRT from a fluorescent tube all quite amazing. Thank you

[fjdarling]

I love your "Engineers Lab." It looks just like mine. I have a Sencore scope too.

Your experiments building building Vacuum tubes and CRT's are very interesting. Do you calculate plate and grid size for your "valves?"

How did you develop the characteristics for your CRT and circuit design?

Enjoy you videos!!!

Thanks,

[zinckensteel]

Excellent! I think it could benefit from a focusing coil, though, to shrink that dot size a bit.

[dalekmoore]

Great work ! have you done any more on the CRT you could pretty much make a scope from your work bit of focusing in fact if i had your skills i would make a CRT tv with the home made triodes for the circuit and CRT ....a monitor would not be impossible from what i saw .

[vataslab]

Do u have a video about building this small crt?

[jonnathandiaz]

Such a nice transconductance tube tester, I would like to know if you have already made the scale of the meter and could you share to us please. Thank you

[Bishka]

Have you tried using a unijunction Transistor? Something ike a BF33F or 2N2420 you can take the scan voltage off of the Emitter and the blanking pulse from either of the bases.

2N2420 seem few and far between these days but BF33F's are readly available on eBay.

[FrankyFixIt]

When I grow up i want to be like JD! Lol My fav channel now ur awesome ty👍👍

[jmcalcote]

@jdflyback - your channel is so interesting to me, even though my electronics background never got past hobbyist stage. Frankly, most of the reasons you do what you do are well over my head. Nevertheless, I’ve subscribed because it’s so fascinating. Suggestion: start a beginners series where you describe some of the theory behind what you do. For instance - vacuum tubes - where did you learn about all this 60’s tech? Id love to learn, but I bet you can’t find most of it on the internet.

[TugAndThugComputing]

WOW! Fkn amazing! It actually produces a picture. Are you selling one by any chance?

[-ElectroMan-]

Wow! That's amazing! I found the CRT particularly impressive. What type of transformer did you use for its 'Blocking Oscillator'? I am planning on building something similar. Thanks so much for sharing!

[joeblow]

would have been neat to watch your own YouTube videos on the crt. but very cool

[muhammadhumza]

Hi,
As a retro gamer who loves using CRTs for retro gaming you did a very nice job. I have a request which is that please bro make a CRT which can be practically used with a Computer or console. The reason I'm asking is because you have guts for it. You are very talented. I know it's not an easy job but bro please think about it. Thanks