Oscilloscope homebrew pt 7: about the hor. and vert. amplifier and its HV Voltage, a DC quadrupler
Part 7 of the series of video’s (with schematics) about how to make a simple osciloscope. Please read the description first. Tube = B7S2 or any other CRT with static deflection, working on 800 Volts (maximum 1000 Volt, at say 500 Micro Amp.... ) between Cathode and Anode.
Anode (+) is grounded, to earth, zero, and the cathode is connected to the minus (-) of the High Voltage generator, giving out say 800 V DC, via a properly isolated wire. More in the earlier video.
And watch the earlier video’s about this subject, links are in this description. Also regarding the disclaimer. Say: the safety risks in terms of health when working with high DC Voltages, say all above 60 DC Volts.
This is (again) a disclaimer, because the high voltages that I am talking about are, again, quite high, though not very powerful (all-in the 1 mA-10 mA range).
Part 7 of making a very simple oscilloscope, for measuring purposes. In this video I show how the DC Voltages (order: 100 V DC up to 180 V DC, current: 100 uA (Micro Ampere) up to 500 uA (Micro Ampere) are made.
Please note: such a CRT tube with electrostatic deflection only need Voltages in this order of Ampères/current: 500 Micro ampères and in fact that relies to all (!) plates (hor. and vertical and brightness and focus grid) inside such a CRT Tube.
We are talking, in fact, about (say) “static high voltages”, with extremely low power, inside such a CRT.
Thus you can use resistors in a voltage divider (to serve all the exact voltages that such a CRT Tube needs) in the order of 1 Mega Ohm (=1 Million) range.
Say a voltage divider at 1000 Volt DC out at say 1000 Micro Ampères, used with 4 resistors of 1 Mega Ohm in a row of 4, can/will give you 4 (or 3) Voltages in the order of ¼ x 1000 Volt = 250 Volt, all-in the 200 Micro Amp. range. Via that you can easily serve such a CRT. More info in the earlier video’s and on schematics on the www/Google.
Because YT blocks/hinders me that I give links to my older video’s when I uplaod a new video, I have to upload the links completely anew, inserting them again. That takes time & effort, anyway. Thus: sorry when the earlier relevant video’s about this oscilloscope will not pop up directly (with their links) in the description/textbox.
The video shows:
(a) how to make the circuit that makes the dot on the CRT screen move from left to right, via a 50 Hertz AC voltage in the order of 100-200 Volts AC. Via a potentiometer you can stretch that horizontal line out, going beyond the horizontal borders of the CRT tube. Schematic is showed.
(b) How to make a Voltage quadrupler out of a 24 Volt 50 mA (nominal, open voltage is 31 Volt) realizing (say) 175 Volt DC at (say) 10 mA (1/4 x 62 mA= say 10 mA) to make the dot on the screen up and down. But: same usable for the horizontal amplifier, thus the time base/sawtooth generator, between say 1 Hertz and 50 KC. Schematic of the Voltage Quadrupler is showed.
And, again: about the disclaimer: I want to refer to the earlier video about a few days ago. Watch them, when you want to work on High Voltage circuits, be it AC or DC. When you don’t have an idea about this: do not make these circuits, for your own safety.
NB: there are thousands of video’s on You Tube where this safety aspect is completely disregarded, I don’t want to belong to them…..(!).
Earlier relevant videos:
First video (21 November 2025) is here • Electrostatic Cathode Ray Tube B7S2 from E...
(link made not visible by YT-Google, had to be re-uploaded, 11 dec 2025)
Second video 25 november 2025 video is here : link not made visible by YT/Google
Third video 28 November 2025 is here • Oscilloscope homebrew pt 3 (to test electr...
Fourth video 2 December 2025 (safety aspects) is here
• Oscilloscope homebrew pt 4: how to make th...
5th video (5 dec. 2025, safety aspects) is here: • Oscilloscope homebrew pt. 5: first practic...
6th video (7 dec. 2025) is here: • Oscilloscope homebrew pt 6: importance of ...
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