Oscilloscope homebrew pt. 5: first practical use in the 1939 way (frequency comparison, time=50Hz)
Please read the description first. And, say, watch the earlier video’s about this subject, when you want more information. Links are in this description.
Further developments are here (10 dec. 2025) • Oscilloscope homebrew pt 7: about the hor....
Part 5 of making a very simple oscilloscope, for measuring purposes. In this video I show 1 first practical application of such a simple oscilloscope setup.
Without the say standard sawtooth wave time base generator. Now a sine wave of 50 Hertz is used as a horizontal line generator.
By comparing a sine wave of 50 Hertz (say 100 V AC) to the horizontal deflection plates and, at the same time, sending in an AC 12-20 Volt sine wave signal in the order of 300 Hertz and 50 Hertz to the vertical plates.
According to that 1939 book (=physics) we can see the relation of these 2 frequencies. By counting the amount of sine waves seen tolling around on the screen and compare them to the 50 Hertz (sent to the horizontal plates) we can “see” how many times that “unknown” frequency (on the vertical plates) is higher, compared to that horizontal 50 Hertz (=50 periods). I live in the Netherlands, so we have 50 Hertz (=periods) mains here.
And yes (of course) this 1939 book was right, because this is all standard radio/electronics/physics theory, brought to visible practice.
A few important remarks/corrections:
1.39: I say “when you do not use (=leave open) that ”pre-acceleration grid” of this CRT tube (the B7S2, pin 12) it also works” and that is true (was tested). In general that is true for other CRT tubes with static deflection that are/were made in the same way (was tested, in an earlier oscilloscope project I also did not use the pre-acceleration grid). But it works (perhaps, now, in this case) somewhat better when you connect it, conform the schematic, inside that voltage divider going from anode to cathode.
In general (when you do not want to use a pre-acceleration grid of a CRT) connect it directly to the Anode (+, here on earth/ground is thus ”0”) . If so: both pre-accelaration grid and anode are on the same potential, attracting the (-) negative electron beam with the same force to hit the CRT screen.
The optimum DC voltage and current to serve the transistor HV oscillator proved (in this case) to be 8 Volt at (say) 350 mA. Thus (say) 2.4 Watt is enough to make such a CRT tube (say 800 V DC anode voltage in the Milliampère, say 1 mA (=1000 uA), or even on smaller Micro Ampères (say 500 uA-750 uA) range) work.
CORRECTION (!!) On 5.08-5.10: Of course the frequency to be tested is/was/must be connected to the VERTICAL (!) plates of the CRT, that is, of course, clear when you know something about how this works. And that is easy. Thus not to the horizontal plates, they are (in this case) driven by 50 Hertz at say 90 Volt.
Referring to my book (where two CRT schematics are showed, for static and e.m. deflection): it is on the website of LULU. LULU id. nr. is 10469565. And ISBN 978-1-4476-1164-6.
Important to tell: When you have bought my book, go to page 49, where I show the schematic of the 4 transistor HV generator, to serve a flyback transformer (or another typical HV transformer with a ferrite core). To bring the frequency up to (say) 16 KC that such a transformer needs (= to get the ideal High voltage out and a perfect horizontal line on the CRT, without intermodulation and thus without interruptions) I soldered a 47 uF (24 V) electrolytic capacitor from the ground wire (minus, zero & anode +) of the transistor unit to the base of the second transistor (looking from left to right) in the first Darlington pair.
Earlier relevant videos:
First video (21 November 2025) is here • Electrostatic Cathode Ray Tube B7S2 from E...
Second video 25 november 2025 video is here • Oscilloscope homebrew pt 2 : a first basic...
Third video 28 November 2025 is here • Oscilloscope homebrew pt 3 (to test electr...
Fourth video 2 December 2025 is here
• Oscilloscope homebrew pt 4: how to make th...
My You Tube channel trailer is here: • Radiofun232 on YouTube, find working & tes...
Type there the keywords that you like (e.g. radio/audio/amplifiers/test/filter/) in the “looking glass” = search function” and give “enter”. Via that you can find specific video’s (under the say 1600 published). 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. Or https://www.lulu.com/search?adult_aud... I keep all my YT videos constant actual. Upload 5 December 2025
NB: the Sine Wave Generator schematic that I have used here and can give (say) 20 Volt AC out is in this video of 9 nov 2022: • Easy 2 transistor Wien Bridge Oscillator 4...