EJK's Marx Generator
I have begun planning for what might be the final incarnation of my Marx Generator adventure. I plan for this new device to be extremely well-built, and have created a preliminary 3-d model of it (Thanks go out to KPovModeller and Povray!) shown below. The new device would be 4 feet long and 1 foot wide, with spark gap mounting rails made of 2x2s. There should be space for 12 stages, even though I only have 11 capacitors at the moment. I plan to use a new charging circuit with a pair of 12KV Neon Sign Transformers connected to generate peaks of 33KV. With my existing 11 capacitors and assuming that all else goes perfectly, the peak potential should be 370 KV. It might approach 400 when I add the final cap.

I am slightly apprehensive about how well my capacitors can handle being charged to 33KV before firing. God only knows how the dozens of R-C-L circuits formed upon discharge will interact and to what extremes voltages might swing. When they reach 33KV, each cap will old roughly 1 joule of energy, for 11 joules total. If the device discharges itself in 25 nanoseconds, the peak power would be 480 megawatts. Now that I know what I'm up against, I'm going to be smart and place a number of high-voltage resistors between the marx generator and NSTs.

This new (final?) Marx Generator won't be cheap - I've calculated that I'll be buying $19 of nuts, bolts, and washers to make the rail assemblies. The capacitors I use go for roughly $25 each after shipping, which is $300 worth of caps (Most of that's already spent - I only need 1 more). The wood will probably cost another $20 or $30. Two 12KV NSTs will probably go for $30 each + shipping. The last thing will be a small armada of high-voltage resistors and diodes, another $15 or $20. All in all, probably $120 worth of material. But it will be well worth it to have something I can be proud of!


It appears that the monstrous powers generated by Marx IV killed more than the variac voltage meter. After achievable sparks kept getting shorter and shorter, I realized that it had shorted out my NST also. Until I can find a way to stop the power spikes from going back where they came from, and I have no reason to think they stopped at the variac (!!!), this project is on hold :(

Marx IV
The fourth iteration of my marx generator. This one has all the spark gaps mounted properly in wood, and space for 8, possibly 9 stages. Now that the rest of the capacitors have arrived, I have installed 7 of them and placed inductors between them.

On the first test with 7 caps, the device threw enough energy back into my variac that there were loud power arcs over the inside of it, and I felt the control knob jump in my fingers. I tried winding 6 inch long inductor coils between the NST and the Marx, and it helped a little but not nearly enough.

As of October 7th 2005, Marx IV has claimed it's first victim. On a test where it generated 4.5 inch sparks, the voltage meter in my variac exploded. It was a loud POP even through my heady-duty earmuffs. I still have no idea how the power fed back all the way to the variac through a pair of 6-inch long, 1 1/8 dia inductor coils and then the NST itself, but it did. Rest in peace, power meter - you were already dead, but now your circuit board is charred and is missing components. Without you, I will never accurately know how much voltage the variac is generating again.

Marx III

The incredibly loud Marx III. This is the same basic thing as Marx II, but with real spark gaps made out of 1 inch, round-topped carriage bolts and a 4th stage.


The 4-stage Marx III fires. So far, it's made a discharge 9 centimeters (3.5 in) long. Unless you want to damage your hearing, you need earmuffs. Red goggles to reduce the blinding intensity of the light are a good idea too.

Marx II I've completed the first parts of Marx II. I've finished winding three inductors (~90 turns, 2 inches long, .5in radius), which have ~90 microhenries of inductance. This is enough to permit the generator to work well up to the 5-7KV/stage region.

Here are pictures of the new style inductors I wound for Marx II. There are now a total of 7 of them - 6 used between the caps, and one to buffer the NST from the marx discharges (not that it could do much good, but...). I counted the turns when I wound one, and it's closer to 100 than 90. That implies 102.3 uH, due to the slight differences between them probably best to just say an even 100uH.

Marx I
I began work on a marx generator. This was nothing intended to be high-quality, it was to be a proof of concept to make sure that my plans were sound. As it turned out, it didn't work very well at all. Except at extremely low voltages (only a few KV in), the inductance of the coils was far too low.