30kV DC Power Supply (homemade)

This is my DIY high voltage power supply. It puts out up to 30kV DC and expects to be fed by a source giving 0 - 24V DC. The input is through banana plug connectors. I usually feed it using my homemade 24V power supply but as shown below, I've also used a wall adapter and a laptop power supply. Also below is a video showing step-by-step how to make this high voltage power supply along with some demonstrations.

Completed DIY/homemade 30kV high voltage power supply.
Schematic for 30kV high voltage power supply.

One modification I made is to make the FOCUS HV output from the multiplier (in this case also called a tripler since it triples the voltage) available. With the 30kV output wire I could get at low as 4kV but I wanted lower. So by making the FOCUS HV output wire available as an alternative I was able to get the range 1.2kV to 4.6kV.

It uses a flyback transformer to step the input voltage up to around 10kV AC and then feeds this into a multiplier which brings it up to around 30kV DC. I've looked at the output on my scope and it's fairly flat.

The flyback transformer was purchased from Don Adsit's "The Experimenter's Store" (which seems to gone from the web). I actually purchased two of them but burnt out the first one when I tested without the multiplier hooked up yet. Don sent the flyback schematics along with the flybacks and on the schematics it gives the resistance across various parts of the flyback secondary. Using an ohm meter you can easily test whether the secondary of the flyback is any good. After I ruined my first flyback one of the segments of the secondary measured infinity (the wire was clearly broken). So make sure you get those schematics!

For the primary of the flyback I removed the wire that came with it and put on my own wires as per the schematic and as shown in the following photo. After wrapping the wires into place and taping them with black electrical tape, I then coated the result with a few layers of black liquid electrical tape for durability, gluing the whole thing.

New wires as per schematic.
Modified secondary/output wires on flyback transformer DIY/homemade 30kV high voltage power supply.

The multiplier was ordered from a local electronics store and is NTE 521 from NTE Electronics, Inc. It has two inputs (hot and GND) and two outputs (focus and the 30kV output). NTE supplies a thick book of all their semiconductor parts (available at any store that specializes in NTE parts) and the schematic for the multiplier was in the book.

Top/front view. The weird clear plastic extension on top is because my flyback and multiplier were taller than I orignally expected. The 30kV HV output is the red wire at the top left of the picture.
Completed DIY/homemade 30kV high voltage power supply - top view.
Front view showing the transistors and the heat sinks. The input is via the banana plug connectors on the right.
Completed DIY/homemade 30kV high voltage power supply - front view.
Top view showing the insides. The multiplier is the beige rectangle near the back and the black thing just below it is the flyback.
Interior of the DIY/homemade 30kV high voltage power supply.
Side view. The round black thing is the secondary of the flyback. The multiplier is to the left of it.
Interior of the DIY/homemade 30kV high voltage power supply side view.
View from the rear showing the transistors better.
Interior of the DIY/homemade 30kV high voltage power supply showing the transistor wiring.

Click here for full details of where I got the heatsinks and how I mounted the transistors to the heatsinks.

I attached a small round brass ball to the end of the HV output wire. Here the end of the output wire is sitting taped to a roll of masking tape to keep it off the floor. The red tube thing is a Fluke 80k-40 40kV high voltage probe which I can feed into my multimeter to measure the voltage.
Close-up measuring the output of the DIY/homemade 30kV high 
      voltage power supply using a Fluke 80k-40 40kV high voltage probe.
My multimeter is on the right. To the left of it is my 24V DC power supply. The output of the 24V power supply is feeding into the 30kV power supply which is on the left. On top of the 24V power supply is a Variac. In this picture I am measuring the output of the entire setup.
Measuring the output of the DIY/homemade 30kV high 
      voltage power supply using a Fluke 80k-40 40kV high voltage probe
      hooked up to an analog meter.
As I turn up the voltage using the Variac, the first reading I get from the 30kV power supply is this one, around 12kV. The meter is on the 30V scale and is showing 1.2V (12,000 volts / 1000 (due to the HV probe) / 10 (due to being on the 30V scale) = 1.2 volts). If I then turn the voltage down gradually I can actually get less voltage. I think I went as low as 4kV at one point. Then it just drops to 0.
Voltage on the analog meter when measuring the output of the 
      DIY/homemade 30kV high voltage power supply.
Here it is at the highest I was willing to turn it up, 28kV, for fear of damaging something.
Highest voltage I was willing to go to on the analog meter 
      when measuring the output of the DIY/homemade 30kV high voltage 
      power supply.
Showing the arrangement for using the 1.2-4.6kV FOCUS wire. Notice that both wires have brass balls attached to them since both have to be discharged after use.
Making use of the FOCUS from the voltage multiplier part of the
      DIY/homemade 30kV high voltage power supply.

Feeding it 0 to 24 volts

As the above circuit diagram shows, this needs a 0 to 24 volt power source to feed it. I usually use my homemade 24V power supply but as the photos below show, I've also used a small wall adapter and a laptop power supply as well. The wall adapter has a switch for selecting the voltage, from 1.5V to 12V. The laptop power supply puts out only 20V and keeps it that way, even if I plug it into my Variac and try to control the voltage that way.

Homemade 24V power supply as 1st stage.
Using my homemade 24V power supply as the 1st stage for
      my high voltage generator.
Wall adapter as 1st stage.
Using a wall adapter as the 1st stage for the high voltage
      generator.
Laptop power supply as 1st stage.
Using a laptop power supply as the 1st stage for the high voltage
      generator.

Video - How to Make 30kV High Voltage Power Supply

Here's my video showing step-by-step how to make this power supply. I also demonstrate it flying a lifter/ionocraft both using my homemade 24V power supply as the first stage and using a laptop power supply instead, which more people have access too.

Video - Fixing my High Voltage Power Supply

While experimenting with ion propulsion added to a Star Trek Enterprise model I broke this power supply for the first time. I could have avoided it if I'd followed my own advice and put around 250 kilohms of resistors (2 watts) in series with the output, but I didn't and ended up damaging one of the transistors.

The following video shows my steps in finding and fixing the problem.

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