Talking about a Cathode Ray tube with static deflect: how to get it working, the DG 7-32 (VLOG) pt 1



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Please read the description/textbox first. Video where I show how a cathode ray tube with static (thus not electromagnetic) deflection works.

The electron beam (negative electrons) is emitted via the cathode and then first focused via a tube-like electrode inside the tube (equipotential focusing, focus “grid”, no grid, it is a tube like structure).

After that the beam is electrostatically deflected via 2 sets of plates, the horizontal and vertical plates positioned inside the tube. After that a sharp focused “electron dot” meets the fluorescent screen on the inner side of the cathode ray tube. The fluorescent material lights up.

The electron beam can be pinched off (pushed back) by negative voltages on the so called “Wehnelt cylinder”. Thus adding a negative voltage (in a certain range) to that, it makes the screen “dark” (or not), the brightness control, often realized by a simple potentiometer in the 500 K-1 M range.

Focusing the dot? Same solution, simple potentiometer in the 500 K – 1 Mega Ohm range.

The sharp dot of that electron beam hits the screen on the inner side. We see it from the outer side, when the fluorescent screen lights up.

We see a bright dot on the screen appear. Or we see a line when that dot is deflected by quickly changing static voltages (between + and -) on the horizontal deflection plates.

That deflection is realized by the time base generator, that is a sawtooth wave generator acting between 1 Hertz (or lower) to (say) 500 KC or 10 MC or higher, etc.

The precise/useful horizontal deflection frequency depends on the signal that you want to study (make visible) via that sawtooth frequency. While, at the same time, a signal is added to the vertical deflection plates. When that vertical signal is HF or VHF it must match with the time base signal. That time base thus can be/has to be triggered by the frequency of the signal on the vertical plates. So that the signal to be studied stands still on the oscilloscope screen.

B.t.w. the vertical deflection plates are the plates that normally have the highest distance to the screen. By that way smaller voltages on the vertical deflection plates can be used, to give a (somewhat) higher vertical deflection of the electron dot on the screen (realizing best sensitivity).

CORRECTION: perhaps better solutions can be gained by swapping what I name as "horizontal" but on the other hand: both sets of deflection plates are extremely sensitive (watch the Philips datasheet). More info to come.

Precise schematics in my book: "Schematics 3, transistor switches, generators and cathode ray tube circuits". Available on the LULU website. Or via ISBN 978-1-4476-1164-6. (author Ko Tilman). On the pages 32 – 53 you will find more info. Oscilloscopes going to 15 KC and 40 KC max. They do not (!) go to higher frequencies.

One schematic with the obsolete DG 10-6 (electrostatic deflection, tube of the 1950’s) and one with an electromagnetic deflection cathode ray tube out of a computer monitor, a tube from the 1990’s.

That black & white tube was the M29EAA2GR. In fact: any B&W tube (screen width say 20 cm) is usable. Deflection currents are driven through the coils around the neck of the tube, max usable frequency = 15 KC (Kilohertz).

Earlier video’s https://youtu.be/cUTJiqKWdJ8 (video about the homebrew 2 Hz-40 KC oscilloscope)

And: https://youtu.be/4V3IXhTFqIM
That was an experiment that was halfway successful…

The deflection coils of that electromagnetic cathode ray tube were driven by a 2 x a 1.5 Watt audio amplifier.

Schematic of that DC amplifier is on my YT Channel. https://youtu.be/jU6VI2WpGqk

My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.

My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.

https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=Ko+Tilman I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube.

Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 1 October 2022.


For people that can read the Dutch language: in my book (Dutch text) “Eenvoudige analoge elektronica deel 2, voedingen en meetapparaten” on page 125 – 148 I have published the two earlier mentioned oscilloscope circuits with a Dutch text. Text is the same compared to the English text, by the way.
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