Equipment - 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 feed it using my homemade 24V 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.

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.

Front view showing the transistors and the heat sinks. The input is via the banana plug connectors on the right.

Top view showing the insides. The multiplier is the beige rectangle near the back and the black thing just below it is the flyback.

Side view. The round black thing is the secondary of the flyback. The multiplier is to the left of it.

View from the rear showing the transistors better.

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.

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.

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.

Here it is at the highest I was willing to turn it up, 28kV, for fear of damaging something.

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.