Caution - High voltage. Keep away from children and pets. I am not responsible for any form of harm done to yourself or others.

So, having said that, I always wanted to adapt a fly swatter to something more serious. Standard electric fly swatters handle what I think to be about 600 to 1000V, this modification would be in the region of 20.000V. Next to that it doesn't require hardcore technical stuff. I wanted to make a cockroft walton generator (which I think is in this module), but that was more expensive and a lot more work. So here is an easy mod by using a cheap ebay component.

Step 1: Parts

The main part I used was a high voltage generator from ebay. With the following stated properties:

Input voltage: DC 3 V to 6 V Input current: 2 A - 5 A High pressure type: the type of pulse current Output voltage: 400000 v(Please pay attention to safety) High pressure discharge distance between: 10 mm - 20 mm

Although they state 400.000 V, this is probably not true. The maximum discharge distance is indeed about 20mm, so that would correspond to roughly 20.000 V, or lets say 10 to 30 kV. Still quite high though. Also they state not to operate it constantly for a long time since it might overheat.

So as an input you could use the standard 2x AA in series or a single 14550 Li-Ion battery (ranges between 3 to 4.2 V, can handle a few amps) and a battery spacer such as some tin foil wrapped with tape. Input stated is 3 to 6 V, but I did also try two lithium cells in series (ranges from 6 to 8.4V) in it, resulting in a much higher discharge frequency. However I would not advice doing this since it might fry the components.
Heat shrink tubing or something similar.
Solder for a neat job, or twist wires together for quick and dirty.
Tools such as soldering iron, pliers.
Fly swatter

Step 2: Strip Insides

First of all take out the batteries. Although I didn't do this for some reason, it would have been very smart to do that beforehand.

Next cut all the wires to the old circuitry. Note that you will need a switch, so if possible leave that in place (mine had that option). Next make sure your high voltage generator fits. I had to remove some plastic with wire cutters which was quite easy. Unfortunately no pictures of that. Next put it in.

Step 3: Solder Connections and Insulate

Solder the wires to eachother in a straight line. Make sure to put the heatshrink tubing around the wire before soldering. I used a double layer to be sure it insulated properly, high voltage needs good insulation.

Which wires should go where can be found in the discription from where you buy your generator. With mine the red was +, the green was - and the two translucent red wires were the high voltage wires (polarity doesn't matter). So I soldered the red wire to the positive terminal of the battery, the green wire to one of the terminals of the switch and an extra wire (taken from the original circuitry) from the negative battery terminal to the other switch terminal. These do not necessarily require insulation if they can't move, if they can insulate them.

On the high voltage side the translucent wires should be soldered to the screen. In my case there are 3 screens of which the middle screen has the opposite polarity of the outer two. Therefore the 2 yellow wires (outer screens) need to be soldered to one of the high voltage wires and the red (inner screen) to the other high voltage wire.

Step 4: Put It All Back Together

Put the wires in a place where they might fit and screw it all back together. Insert batteries, apply warning sticker and have fun! Make sure not to zap persons. I don't think the amps are high enough to kill someone but hey better not try.The weird smell you get when you use it for some time is actually ozone being formed by passing the high voltage arc through the air.

Questions? Feel free to comment or send me a message in either Dutch or English.

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