How to find out the wiring of unknown (HV) transformers? (Part 1)

Please read the textbox first (the warning regarding High Voltage circuits!). My camera stopped suddenly, so I had to name this “part 1”.

Anyway: a video about how to find out the wiring of unknown transformers, say bought on radio flea markets.

Here the primary coil of a 16 KC line transformer is measured and find out.

Important/strange: between pins 3 and 5 there seems to be a shortcut in the showed schematic (!) but the measurements are “as they are” (…). These strange things happen, kind of "transformer logic".

All (thus) has to be worked out further by getting this 16 KC oscillator into service + to find the best 2 coils with their central tap (watch the schematic) to which these 2 Darlingtons of 2 x BD 139 can drive out the HV coil at its utmost HV voltage, say 2000 Volt on 16 KHz, the natural resonance of this ferrite HV transformer unit.

I talk about finding out primary windings of unknown transformers. That is a very broad range. Transformers (unknown or well known) could be made to be connected to (say) 230 V AC or 110 V AC (50 Hz/60 Hz). But also to supply sources on other frequencies, here 16 KC.

In case of an old school HV oscillator on say 16 KC for a cathode ray tube such an oscillator can be supplied by any DC voltage. Look at (say) old school cathode ray tube B/W or color television sets, their supply voltage is in general DC, made directly out of the mains supply, 110V or 230 V, 50/60 Hertz. For portable (old school) analog TV sets the 16 KC line oscillator (driving the HV to make the cathode ray tube to light up) often was supplied via 12 Volt DC.

Whatever that may be: primary windings/coils on an unknown transformer are often the most problematic to be found out, but with (say) a transformer with many coils on the secondary (!) that could also be problematic. Though the things that I show here (DC measurements and their DC Ohms value ) and finding out the (probably) different coils and taps could work very well. Take a very close look on your Ohms meter an always shortcut the test wires first + align the meter to “zero”.

So you can find out: (more in part 2 of this video)
Part 2 (video 2) is here https://youtu.be/5i2EtkBltA4


1. How many coils are on that primary/secondary
2. Their DC resistance (please note: their AC resistance differs on the frequency where they are used, more video’s about this issue are on my YT Channel, here it is 16 KC/AC meaning that their resistance in my oscillator will be higher)
3. How to find out coils that have a central “tap”
4. Where that central tap is (the electrode)
5. Where the “ends” of the coils that work with a central tap are
6. Which coils have a tiny diameter (in terms of copper resistance), that is done by looking to the electrodes to which they are soldered. Could give an idea for the maximum current that such a tiny wiring/winding can endure

7. Only in cases of a HV oscillator: thick wires are often more usable to be driven with a high/higher current to get the maximum output voltage in the HV coil

I have given in this video a schematic of a HV generator that I made once to supply an old school black and white cathode ray tube of (say) 30 cm diameter. It worked properly.

Warning: be very careful with HV oscillators. Avoid/block that children of people with heart problems or elderly or people with a pacemaker can get into contact with that HV wire and/or an electric fence/HV wire, be it giving out AC or DC.

All voltages higher than 60 Volt are potentially dangerous! (standard safety used in old school telephone lines).

There are more than 1000 Video’s on my YT channel. I only do analog electronics: audio amplifiers, analog measuring devices, radio circuits, many Shortwave radios, many oscillators HF and audio, other audio & shortwave circuits.

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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 12 August 2021.

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