Please read the description/textbox first. Disclaimer: don’t make this circuit when you are a heart patient or have a pacemaker, when you are a child, when you have no or less experience with electronics or electrical circuits or have no idea about safety issues in electrical circuits.

IMPORTANT: to safeguard the circuit, supply it via a 30 Ohms/10 Watt power resistor. If so, your transistors in the oscillator circuit will not burn out. That was tested experimentally.

Be very careful with these circuits: that 500 Volt out (AC or DC) is dangerous. Do not touch it with your hand or other parts of your body.

Keep the supply voltage of the oscillator low (5-14 Volt), in that case the HV output voltage will also be on the low side of the dangerous (AC, 14 KC-50 KC) spectrum.

The oscilloscope tube that I want to use (the DG 7-32) only needs a tiny anode current at 500 Volts DC, say in the order of 30 Micro Ampère (!). (that is 30/1000th of an Ampère). That is a static voltage without real power.

The screen dissipation is approx. 2.5 Milli Watt. That is all very very tiny in terms of electrical power and safety risks. Correction: on 8.36 I of course mean to bring the voltage down (not up!). More video's to come about this very very simple oscilloscope. Takes time. 5 oct 2022.

Next video 5 0ct 2022 is here [ Ссылка ]
Next video 6 0ct 2022 is here [ Ссылка ]

This 3 Oct 2022 video does NOT show a “ready made” electronic HV circuit. It only shows the effects of changing the supply voltage on:

A) the output power (AC out on the HV coil)
B) the frequency where it works (14 KC-50 KC or even 60 KC)
C) the frequency and supply voltage where it works best. So: the highest AC voltage out on the secondary coil, given by the lowest possible supply current/voltage at frequency “X”
D) the waveform, its purity and (preferred) lack of harmonics that can/will have an effect on how the oscilloscope tube (now the DG 7-32) will work in practice.

This (D) is a serious issue. Key issue: smoothing out harmonics and “taming” wild oscillations. Many electronic cures can be used for that purpose (“damping”).

1) Important: this is a circuit that always works, because we use an end- Darlington to drive the HV coil (BD 139 Hfe = 140 and a BD 743 C Hfe=40) and a BD 139 (80 Volt transistor with a high Hfe of 140-150) in an A stabile Multivibrator circuit. The 2 capacitors in the circuit (here 4N7 = 4700 pF) play a very important role, responsible for the frequency. With 2 x 10N it goes to a lower frequency range and with 2 x 100 N even much lower frequencies are realized.

2) Important: When a HV transformer in an oscillator circuit is “loaded” too heavy on its secondary winding (via a resistor, a capacitor, or both) these effects occur: (A) the frequency goes down, (B) the efficiency goes down or can go down, the output voltage drops too much (C) a no longer logical current (in terms of wattage) is visible on the power rail (here 0-24 Volts) and at the primary oscillator coil (thus: instability, strange parasitics of all kinds)

Also important: this setup (schem) does not only work with typical 16 KC old school line transformers, other transformers can also be used, preferred ferrite transformers.

Feel free to experiment with other types of transformers. Key issue: the A-stabile multivibrator must ideally work on the (typical) resonance frequency of the transf.

That can be set/found out by experimenting with diff. coupling/backcoupling capacitors (here the 4N7). For “reversed” small (max. 10 Watt) mains transformers (110 V-230 V at 50 Hz or 60 Hz) with steel laminated cores the ideal frequencies (somewhat resonance-like) to get the best HV out are in the order of 200 Hertz to 800 Hertz. Test capacitor for a first test to get this working in that frequency range (lower than 1 KC): 100 N (=0,1 uF), a 100 Volt type. Perhaps 220 N (0,22 uF). Try & test.

My You Tube channel trailer is here: [ Ссылка ] 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”, etc.

More info:
[ Ссылка ]
(2 October 2022, HV trafo)
[ Ссылка ]
(1 October 2022, about the oscilloscope tube)
[ Ссылка ]

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

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. Upload 3 October 2022.

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