jacob’s ladder

I cleaned out the junk room this weekend and found two old tube tvs, so I cracked them open and salvaged the flyback transformers.



(If you do this, make sure to discharge the tube before messing around inside the TV.) It was a rainy weekend so I was stuck inside, so I decided to make a Jacob’s Ladder out of one of the flybacks. I needed a circuit to drive the flyback so I thought I’d try one of the 555 timer circuits I’ve seen online.


I put together the following two different circuits but I couldn’t get either to work.



I finally gave up on the 555 circuits and built a ZVS (zero voltage switching) driver. There is tons of info on the internet about how this circuit works, so I won’t explain everything, but here is the schematic.


I pulled a 60uh choke and a 470nf cap from an old power supply and the fast diodes were B4404s that I pulled from the TV. I used two 1n4742a 12 volt zeners and two K2382 mosfets.



I wound a center tapped primary coil on the flyback and cut up a coat hanger for the V of the Jacob’s ladder.


I powered the whole setup with 24 volts from an old pc power supply.


It fired right up and started arcing.


I ran it for several minutes at a time, constantly monitoring the temperature of the mosfets and they stayed perfectly cool the entire time.