Kaizer SSTC I


This is my first solid state Tesla coil, so I went with a sturdy and proven schematic made by Steve Ward. After all, a lot of other coilers have replicated this circuit with great success and therefore it is easy to find information how it works and how to troubleshoot it.


High Voltage Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm



One of the differences from the original circuit is that I use 230VAC input instead of 115VAC. So capacitors and MOSFETs have a higher voltage rating. I will change the interrupter to be able to go down to a very low break rate.

 SSTC Specifications

Bridge2x IRFP460s MOSFETs in a half bridge configuration
Bridge supply0 – 230VAC from a variac, 8A rectifier bridge and 330uF smoothing capacitor0 – 325VDC on the bridge.
Primary coil115 mm diameter, 1.78 mm diameter isolated copper wire, 10 windings.
Secondary coil110 mm diameter, 275 mm long, 1000 windings, 0.25 mm enamelled copper wire.
Resonant frequencySelf tuning at around 250 kHz.
Topload100 mm small diameter, 240 mm large diameter, toroid.
Input powerContinues Wave mode: 1000 W at 230VAC input voltage.
Spark lengthup to 250 mm long sparks running interrupted.

SSTC Schematic

All unused input pins of a 74HC14 has to be tied to ground, floating inputs and a noisy environment is a recipe for trouble. Therefore noise can get coupled between the gates internally and make the whole IC not work properly.


SSTC Construction

22nd January 2009

I began the construction of the half bridge circuit in a small plastic box, the heat sinks are a Pentium II heat sink cut in half. The bridge is made from copper wire size 2.5mm² / AWG14.

The bridge is made from a 8A bridge rectifier with 330uF 450V smoothing capacitor, two IRFP460 MOSFETs with MUR1560 diodes, two 0.68 uF 400VAC film capacitors for the voltage splitter and 10R gate resistors.

The driver circuit is made on vero board with a external 12VDC power supply.


SSTC Problems and Troubleshooting

23rd January 2009

When I first tried to run the driver circuit separately to test the driver before connecting it to the MOSFETs, it only resulted in the MOSFET driver chips (UCC37321/UCC37322) catching fire and burning up like a small volcano. This did of course upset me when it happened once more when I had changed the chips. This led me to seek help and I learned that running the driver chips unloaded, without a MOSFET or GDT connected to the outputs, the chips will oscillate into oblivion and burn them self down.

With the complete circuit put together it all worked except the primary coil was phased wrong, but it was no problem since I used banana plugs for the primary connections.

I ran the coil as CW (Continues Wave, non interrupted so its switching at its resonant frequency) to stress it to its maximum, which also did result in failures at 230VAC in, drawing around 4 to 5A.

The secondary coil was grounded to the mains ground in my house, but by accident I were using a plug without a earth connection in, so the secondary earth was arcing to the phase and neutral in my power bar. Pushing around 1 kW into this rather small circuit with passive cooling became enough combined with HF noise on the phase and neutral and one of the MOSFETs exploded violently and the other died silently. Here I discovered my design did not make it easy to change the MOSFETs, a important thing to consider in future constructions.

For the next couple of days I could not get the coil to work again. Everything in the driver circuit was changed and measured with a oscilloscope without finding anything out of order. It was first when I by accident measured short circuit connections with a DMM that I discovered one of the secondary windings on the GDT was not connected to the MOSFET, it was because the gate resistor was destroyed from the short circuit of the MOSFETs. Changing the 10R resistor made the whole thing work like a charm again.


SSTC Sparks

Here are some pictures from the first light, input power is from 30VAC to 230VAC at up to 5A.


SSTC Audio Modulation

I use a audio modulator made by the user Reaching (Martin Ebbefeld) from 4hv.org.

For sound input I use a cheap children’s keyboard from a toy store. Its far from perfect for the job, especially because its waveform is highly distorted. It does not deliver clean tones ,but seems to involve a lot of modulation inside it to simulate different instruments. But its cheap and expendable.

Watch the film and look at the schematics for more about the audio modulation.


Building this clone of Steve Wards SSTC5 was a great introduction to solid state Tesla coils. I now have a understanding of how it works from interrupter to driver to bridge.

Further projects with this circuit will be a complete rebuild with audio modulator and a full bridge of MOSFETs, this will be a separate project.


In thew following videos, the SSTC I is playing music from the interrupter shown in schematic for the SSTC II.

87 thoughts on “Kaizer SSTC I”

  1. I wanted to ask you what you think of Steves DRSSTC schematic with the flip flop circuit, so that the interrupter never shuts off the UCC’s. I came up with a way to use another 555 with the feed back as part of its timing instead of the 74HC109.

    does it actually need a “flip-flop” device? because some times the output wont line up and will send out a very short on time


  2. Hey Daniel

    I am only working with his universal driver as Steve called his own older designs for obsolete compared to the new driver.

  3. I am wondering, what is c4 for in the schematic, is it a dc blocking cap or it it used for something else?

  4. Hey Marshal

    Its a DC blocking capacitor that should stop the heavy DC currents from flowing at the rather low DC voltages that the GDT sees. If you have problems with lower values, try using a larger, up to some uF and with a 100nF in parallel, this should take care of resonance in the GDT primary drive circuit.

  5. Hi Mads, I am looking to start experimenting with SSTC’s and was wondering if I could use a 36v supply for the half-bridge if I lowered the primary coil turns and perhaps made the secondary coil a bit smaller. I understand that I will get a much lower spark output from the secondary coil but I don’t mind too much as this would be my first time making a SSTC.

    This 36v supply is 3 12v 7ah lead acid battery’s and I don’t need long runs from the SSTC whilst experimenting so I can afford to allow for a higher current draw in return for using a lower voltage.

    Just wondering if that would work? And would I need to adjust anything else such as C8 and C9 in order to allow for more current to be drawn?


  6. Thanks for that Mads.

    About using mains power, I am waiting until I can find/source a variac before I start using mains power with my projects. I am fine using mains for small low voltage step down transformers or items that have been commercially designed and tested for mains use, I am just slightly wary of connecting homemade circuits to it without a variac.

    Plus I have my parents who don’t like the idea of me doing any electronics, seriously if a light-bulb blows or something happens they always blame me and my electronics! Talk about ignorance right.

    Anyway enough ranting and on to finding a decent piece of tubing to wind my secondary coil onto.


  7. Hello, I want to ask if it is possible to run this design without a variac?
    The question is if it is possible to run this SSTC directly of the mains 230 VAC with a bulb as current limiting for charging the capacitor in the start, and after the capasitor is charged, just bypas the bulb and run the tesla coil directly from mains suply, without using a variac?

  8. Hi Benjamin

    It is possible to run it as you say, but be aware that you have to design it carefully to run at full voltage from day one, doing first light and testing and tweaking a variac will save you some headaches.

    If you don’t have a variac, maybe use a 230v to 48v transformer or something in that manner, for testing, else you just risk a BOOM at full voltage and will have to rebuild and fault find on burned tracks.

    Kind regards

  9. Would the gate drive UCC chip stage work at lower frequency’s of around 50khz (for driving a flyback transformer)? Or would I need to alter the value of the DC blocking capacitor to something larger, as most schematics I have seen that don’t use the UCC chips always use 1uF for this cap.

    Since the chip I am using has out-of-phase outputs (sg3525) I plan on using two of the same chips, would that still work?

    I am basically trying to solve the problem of heating mosfets on my half-bridge since the heatsink for mine gets too hot to touch after a few minutes.


  10. Hey Alex

    The DC blocking capacitor I use here is on the edge of being too small, but its okay for 300kHz. At 50kHz you should properly use around 2uF. We want the capacitor to act as almost a short at our frequency, so if you can keep Xc under 2 Ohm, it should be good enough. (math: Xc = 1/(2*pi*f*C) )

    If you want to go further into detail, look at the series RLC resonant frequency of the capacitor, your working frequency must be lower than the capacitors self resonance, else it will start acting like an inductor.

    When using inverted outputs from your PWM ic, there is no problem with using two of the same UCC drivers.

    Which size gate resistors do you use for your MOSFETs?
    How large is your heat sink?
    How are you driving them in this setup?

    Kind regards

  11. Hi Mads, I gave the chips a try using a 1uF cap and the result was the chips got warm and the MOSFET’s still got hot. a strange thing to note is that as I increased the frequency past around 50khz the primary coil voltage of the GDT would drop, all the way down to 7vac at 85khz.

    I am driving them in a half-bridge configuration, 36v on the bridge and 15v for the logic/gate drive. I am using 22 ohm gate resistors (is that too large for 50khz?) and IRFP260’s, the heatsink is out of an old ATX supply and it has two smaller heatsinks screwed onto it via the spare mounting holes.

    My gate drive transformer materiel is type 77 from eastern voltage research and I have wound the primary and secondary’s using tri-filer windings to reduce leakage inductance. With the MOSFET’s connected the GDT only seems to draw around 40-60mA max (depends on frequency).

    I am trying to get it working with a flyback transformer first before I go ahead and attempt to make a SSTC, but can’t seem to make it work without the heating problems.

    Did any of your half-bridge heatsinks get hot at all after just minutes?



  12. Hi Alex

    A lot of my stuff heats up quickly if I run it on the edge of what I designed it for, your heat sink does however should relatively small as nothing good usually comes out of a ATX PSU.

    Try with 10 or 5 Ohm gate resistors and see if it helps on the MOSFET heating, UCCs do get warm, its a big job done from a little package, true to fix a small heat sink on them if you like, or parallel two of them, put on top of each other.

    Kind regards

  13. Thanks Mads, I will look around for a larger sink. The one I have doesn’t have big fins and the PSU had a fan to help with cooling (it was only a 250w PSU too) if I recall.

    I will give some 10 ohm resistors a try too. One thing I noticed is that one of the chip outputs gives out .2v less than the other one (between output and ground). Not sure why or what affect that could have on the operation of the circuit, I did try a spare chip I have and that was the same. The only thing I can think of is the 0.1uF caps between pins 1, 9 and ground and 2, 16 and ground, one cap is slightly larger by 1nF. Could that be enough to upset the “balance”? They are film caps too.

    Can’t wait until I get my scope so I can actually see what is going on ( : , Just need to decide between Rigol DS1052E or Owon Sds7102.



  14. Hey Alex

    Those are some terrible heat sinks, cost minimized.

    Do you have capacitors across the supply for UCCs? Right next to the IC. 1nF difference should not matter.

    I just quickly looked at the specifications, I have a Rigol DS1052E and I must say that the Owon looks like a better choice.

    Kind regards

  15. Well I tried using 10 ohm gate resistors and it made no difference, still heating up within minutes (this is with-out audio modulation too). I also tried a larger heatsink but it still got hot.

    Yes the UCC’s have decoupling capacitors, .1uF right next to the pins. I’m stumped as to what is causing this. I put my multimeter set to measure AC volts across the drain and source pins of the lower MOSFET and it read 0.876vac as the voltage drop when the bridge had 12v on it drawing around 1.2 amps. Forgot to measure it with 36v though but the current draw is usually 3-5 amps @ 36v. I know my meter is not an accurate way to measure this but I think it gives some sort of indication.

    I guess the only thing to do now is scope the circuit and see what that shows : / . I might have to pay import duty tax on the thing if customs get their hands on it, which is annoying.


  16. Hi Mads, just dropping by your site again to let you know that I went for the Rigol scope in the end and so far it has been an excellent choice. I nearly went for the Owon but it was about £150 more expensive, so I decided since I am only using it for hobby use the Rigol would be more than I will ever need.

    I am just wondering what you use when scoping primary/high drain-source waveforms. Do you use a 100x probe or will a few turns of wire around a high current conductor connected to a probe? Most of my circuits right now are powered by my bank of lead acid battery’s so the scope is the only thing referenced to mains earth.

    Any pointers here would be appreciated, Don’t want to blow this scope up just yet!


  17. Hey Alex

    Excellent choice for a hobby scope 🙂

    I use current monitors from Pearson, they are expensive, but worth it all, you can some times find them cheap on ebay. I got a 101 and 110 model.

    I also got a tektronix 1000 Volt differential probe, then there is no worries about grounding the circuit through your scope. If you can not afford this, you need to have your circuit galvanic isolated from mains and earth the negative rail of the circuit. So there is a prefered grounding compared to currents wanting to flow through your scope probes.

    Kind regards

  18. Very nice coil! Im curious, did you notice heavier kickback to the fets while pulling an arc to ground? Mine run completely cool at 110 mains until I start drawing arcs, and then this start blowing up 🙁

  19. Hey Photonned86

    I have not had any problems like that. It could be that it is just a heavier load on the MOSFETs when you have a direct strike to ground and they simply blow up from excessive current.

    Kind regards

  20. Thank you very much Mads! Is it possible then to saturate a core on the primary to prevent such things? Before I go doing random things I would much rather talk to a professional ;D


  21. I built this design but I made the secondary 15 inches tall instead of the recommended height on the schematic. Could this extra height be decreasing the spark length?

  22. Hey Theo

    The higher Q factor of a bigger secondary coil could result in a worse power transfer, but since this is a half-bridge driven coil it is not a perfect choice for long sparks. How long sparks did you get?

    Kind regards

  23. Jose Luis Rubalcava

    Hi Mads!
    You are made an excellent work to share it, thank you. We are builting SSTC I and do not know, where is antena or where does it plug in?

    could it connect with the stick that touches the spark?

    thanks for read this message and regardS


  24. Hi Jose Luis Rubalcava

    Look at the schematic, the antenna is shown just after the input rectifier and capacitor. The antenna is capacitively coupled to the input of the hex schmitt invter IC, protected by two 1N60 diodes.

    Do not make sparks to the antenna!

    Do not place the antenna so close to the secondary coil that there begins to form corona/sparks from the antenna.

    Place antenna about half way up of secondary coil, and only as close as to make the coil run stable, this will change depending on power level and spark length. Long sparks can make it become unstable as the load from the spark pulls the resonant frequency down a lot.

    Kind regards

  25. Hello, I have some questions about the circuit , my gate drivers when connected to only the gdt get really hot after just a few seconds, I checked with and oscilloscope and they give a wave but if I leave them running for more than a few seconds they get damaged. I’m supplying them with 12V.

  26. Hi Asdfire

    The UCC drivers can not be run open loop, without a load connected. So you need to either have some load resistors on the secondary side of the GDT or connect it to the gates of the MOSFETs.

    When the UCC drivers run unloaded they can start oscillating and will heat up very fast, as you also described, this will eventually damage them.

    Please join our forum at https://highvoltageforum.net and make a thread about your Tesla coil build 🙂

    Kind regards

  27. Hi i know this is old but im hoping you still check it. Im a bit confused about the driver circuit schematic. What is the coil thing on the right side?

  28. Hi Aiden

    I check my website for comments every day 🙂

    The coil is the gate drive transformer, this ensures galvanic isolation from the driver stage to the power stage. All capacitance’s are written in the schematic, if you meant voltage rating instead, its only supplied from 12 VDC, I think I used 50 VDC rated components.

    Kind regards

  29. Hi sorry for all the comments i just want to be sure i’m getting this right as this is my first tesla coil build.

    you can build with without the audio modulation circuit right?
    if you add the audio modulation circuit you connect its output to where the antenna on the driver circuit is?

  30. Also what would you recommend using for the antenna a piece of wire? And how far away should it be from the coil.

  31. Hi Aiden

    Yes you can build it without the audio modulation on.

    The normal interrupter and audio modulator both connects to the same point, the ENBL pin of the UCC MOSFET driver ICs. The antenna connects to the IN pin of the UCCs.

    I just used a piece of regular small wire, about 10 cm from the secondary coil and maybe 10 cm tall. But adjust it either up for more feedback if its not running stable or retract it to be shorter if there is sparks on the top of the antenna 🙂

    Please come join the forum https://highvoltageforum.net/ and show how you are building your Tesla coil 🙂

    Kind regards

  32. Did you buy your gate drive transformer or make it yourself? if you baught it which one did you get if you made it yourself how did you do that and is there any directions you ca give me in this area? ive never dealt with gdt’s before.

  33. just out of curiosity what did you use for the core of your secondary coil? it looks like a cardboard tube.

  34. Hi, I know this is a quite an old article, but I would like to ask a question about the driver. I have built a very similar driver circuit for my Tesla coil, and it works OK, but i am getting relatively small sparks and the MOSFETs seem to be heating up quite a bit at only 10% duty cycle, 330volt bus and active cooling. I have a suspicion that it might be the gdt, since its output waveform is highly distorted (ringing, doesn’t resemble a square wave) and the UCC’s are getting quite hot to the touch. The toroid ferrite core for the gdt is a cheap one from eBay and it’s wound using trifilar 0.5mm enameled copper wire. What do you think ? I’ve read that high permeability ferrite is better, but that general ferrite can be made to work too. Sorry about my English.

  35. Hi Mark

    The GDT is a crusial part and you should not try to save money here, a distorted gate drive waveform will result in the MOSFET being driven almost all the time in the linear region, where there is huge conduction losses.

    I seems you already know what the problem is and it sounds possible that it really is. Check out this GDT waveform troubleshooting guide: http://www.richieburnett.co.uk/temp/gdt/gdt2.html

    Please join the https://highvoltageforum.net/ forum and show off your tesla coils and discuss on how to improve them 🙂

    Kind regards

  36. Hey Mads
    I’m kinda new to Tesla Coil’s and I’ve been trying to build Steve wards SSTC 5, A few question I had was
    If unavailable, Can we use a pin compatible IC without an enable pin instead of the UCC chips, which are not available where I stay. I thought it should still work if we remove the interrupter?
    Also, Why do we use VAC capacitors in the half bridge circuitry and is that also what Steve Ward uses in his set up? He hasn’t made it explicit in his webpage.
    I would really appreciate it if you could clarify my doubts.

    Ravi Shankar

  37. Hi Ravi

    You need a driver IC with enable pin if you want to interrupt it, else it will always run in CW mode which is a much higher stress on the MOSFETs and all components will properly heat up if you do longer run times, like more than a minute.

    What do you mean by VAC capacitors? We use MKP capacitors in almost all power applications as they tolerate the high frequency currents with lower dissipation than most other capacitor types. For a MKP capacitor that VAC rating is less than half of the VDC rating.

    Kind regards

  38. Hey Mads
    Thank you for the reply

    The VAC capacitors I was referring to was C8 and C9 in the circuit diagram.
    I think in your article you mentioned it was 400 volts VAC film capacitor

    I didn’t quite understand their use

    Ravi Shankar

  39. Hi Ravi

    They are used as voltage dividing capacitors to get a center point for the half-bridge. You can omit the capacitors if you tie that end of the primary coil to ground instead. The voltage dividing capacitors are normal practice if you are using a voltage doubler input for the mains.

    Kind regards

  40. Andrew Villalpando

    Hi, I cannot find the 1n60 diode on Mouser, is there any replacement for it? or it must be this one exclusively?

  41. Sebastian Nutter

    Hello, I’ve been having a bit of a problem with my mini sstc setup ( Steve ward based) and maybe you know what it could be. When running the coil at peak power 200 vdc, I noticed misfiring when in interrupt mode. It’s not too bad but noticable ( using irfp250n fets currently ) , I tried a test half bridge of irf740s as I’m in Germany and would like to use full mains power but when reaching input power of 130-140vdc, the misfiring was out of control and I shut down the system. I’ve tried playing around with the antenna thinking that could be the problem but no such luck, also considered the fets being a fault ( will try a test circuit of irfp460 ) it could also be the feedback working from secondary harmonics as I can’t run the secondary with full topload ( I think the secondary is 425 khz, have to look at Tesla map for coil specs ). Any advice would be extremely helpful as you are a Jedi master of sstc circuits !

    Cheers from Germany,


  42. Hi Sebastian

    I hope my skills will come in handy and I can give you a piece of the force.

    It sounds like noise issues, that is EMI in your interrupter circuit. Try to shield the interrupter and cable/wires with aluminium foil as a first try and see if it helps. SSTCs are a bit nasty when it comes to emitting EMI.

    Do you have problems with corona/sparks forming on the antenna?

    Kind regards

  43. Rohith Radhakrishnan

    Hey! Rohith here!
    I’ve a doubt on one of the technical issue you faced while the construction of the coil. That you’ve mentioned under the troubleshooting section. What do you mean by this? Can you explain it clearly so that I would understand it. I’m following Steve Ward’s SSTC Design with all the same components for the design and for the half bridge(MOSFETs) I used a 240v/110v 20W step down transformer since I’m living in India.
    “I ran the coil as CW (Continues Wave, non interrupted so its switching at its resonant frequency) to stress it to its maximum, which also did result in failures at 230VAC in, drawing around 4 to 5A.” (Please explain this once more)
    How did your mains supply fail? Can you explain it clearly?
    Your response would be much appreciated. Thank you!

  44. Hi Rohith

    Continues wave, means that it is no interrupted, so at every cycle of the resonant frequency of the secondary system, the primary system is pumping current into the system. Eventually the MOSFETs failed due to switching losses heating up the die above its maximum operating temperature.

    Kind regards

  45. Rohith Radhakrishnan

    Thank you for your response. A few doubts more.
    Did you use any fuse or any other safety equipment in the circuit? If use, can you mention the rating of such thing and the place you’ve connected it in the circuit.

  46. Hi Rohith

    You can only put a fuse on the mains supply, fuses will not blow before a MOSFET explodes if there is a fault, fuses are not that fast reacting. If the coil could draw 4 Ampere, I would properly use a 8 Ampere fuse, because a Tesla coil can have some large current consumptions on ground strikes.

    Kind regards

  47. Rohith Radhakrishnan

    Thank you for your response Mads.
    What can I do to prevent the failures of the mains supply?
    What’s the purpose of 555 timer IC (Interrupter) that you’ve used? What really happens in the circuit or in the coil if I vary the potentiometer?
    What really determines the type or characteristic of the spark that occur at the secondary?
    Your response would be much appreciated. Thank you!

  48. Hi Rohith

    A solid state Tesla coil is operating on the edges of what is possible for the components in use, it is a very tough job for the electronics, you will have shortened life time on all components in the primary circuit due to high temperature transients during high current switching.

    The 555 timer interrupts the Tesla coil so it does not conduct current all the time, this is to allow the components to cool off between pulses.

    If you want to study arc dynamics, take a look at this great arc simulation discussion: https://highvoltageforum.net/index.php?topic=670.0

    Kind regards

  49. Rohith Radhakrishnan

    Thanks Mads! And one more thing.
    Can you suggest me some good projects that I can do for my final year UG program? Or any innovative ideas? And can you mention some websites regarding all these?
    Thank you!


    hello, i’m having trouble reproducing this diagram, i would like to know how i can test the UCCS (321/322) and 74hc14 to check if they are working properly … the only difference from my diagram is that i replicated the switch based at steve wards’s SSTC 5. the output of my switch is varying 6 and 8 vdc in a square signal, is this a problem?

  51. Maycon douglas

    hello, i’m having trouble reproducing this diagram, i would like to know how i can test the UCCS (321/322) and 74hc14 to check if they are working properly … the only difference from my diagram is that i replicated the switch based at steve wards’s SSTC 5. the output of my switch is varying 6 and 8 vdc in a square signal, is this a problem?

  52. Maycon douglas

    I would like to know if the output of the switch with 8v is a problem for the driver operation. and how can I test the Uccs (3732X) to verify that they are working correctly.

  53. Hi Maycon

    You need a oscilloscope with a band width at least twice of the signal you try to measure, you can not use a regular multimeter for this kind of work.

    Kind regards

  54. Hi i would like to reproduce this circuit but i Have problem with ucc3732x ICs , i can’t get them anywhere locally.
    And really dont want to order from chinq oř something like that.

  55. Hi Robert

    If you want to use an alternative, you have to find some drivers that are inverting and non-inverting and also have a enable pin. Then it is just a matter of connecting the pins correct to that IC.

    Alternatively, you could order from Mouser or Digi-Key in USA, it is however more costly.

    Kind regards

  56. Hi.
    Thank you very much Mads.
    I will try to post some progress info onto 4hv forum but that will be in a month or so when all of the components will arrive.
    Thanks again.


  57. Hi Mads (I’ve been calling you Kaizer – sorry :).

    This is in response to your old post (copy pasted below for reference).

    I found your comment interesting because I’ve recently being playing around with the antenna – different lengths, different positions, etc. I’ve even drawn arcs from the top load to the antenna (big sparks :)) with no apparent negative effects on the electronics. Maybe that just goes to show how resilient the IGBTs are.

    I have 2 other questions that I’ll post in more detail on the forum, but will summarize here too:
    1) I’ve been trying to use a current transformer for feedback instead of the antenna. No matter what I try, it stops working entirely when I replace the antenna with a small current transformer across the bottom of the secondary. It’s even more confusing because when I scope the CT output (when the coil is running with an antenna), I get exactly the output I would expect (resonant frequency of the coil, more than enough peak-to-peak voltage). I’d love to get this to work instead of the antenna because it just feels more elegant.


    **** Your old post ****

    Hi Jose Luis Rubalcava

    Look at the schematic, the antenna is shown just after the input rectifier and capacitor. The antenna is capacitively coupled to the input of the hex schmitt invter IC, protected by two 1N60 diodes.

    Do not make sparks to the antenna!

    Do not place the antenna so close to the secondary coil that there begins to form corona/sparks from the antenna.

    Place antenna about half way up of secondary coil, and only as close as to make the coil run stable, this will change depending on power level and spark length. Long sparks can make it become unstable as the load from the spark pulls the resonant frequency down a lot.

    Kind regards

  58. Hey Mads!
    This is Rohith here. I have an issue with the GDT used for gate pulses, even though i have used the toroidal core that’s been properly wound. It’s not generating pulses. And the other thing is even if i vary the potentiometer, the UCC output that’s fed to the primary of GDT is not varying in terms of voltage that am not able to control the pulses. I have few doubts regarding this, which i have listed below:
    *What is the wire gauge that you have used for the GDT?
    *What should i check in the 555 Timer IC part?
    *What do you mean by “cap sub point”?
    Can you just throw me some light so that i can proceed further on the project.
    Your response would be much appreciated.

  59. Hi Rohith

    Either your UCCs are defective or you are lacking a feedback signal for them to enable on and give an output. You can try to just pull the ENBL high to see if you get the 555 timer output pulses.

    I use regular CAT5E network cable for my GDTs

    Where did you see me write anything about “cap sub point”?

    Kind regards

  60. Hello Mads

    Perhaps I am missing something, but between your SSTC III bridge schematic and the ExpressPCB PCB drawing you link to in an above comment, I think that the Bridge Rectifier D3 has gone missing.
    Looking at the ExpressPCB drawing it appears that you apply up to 230VAC directly across C12??

  61. Hi Slim

    Thank you for asking about that apparent error in the PCB file, it should be labelled 320 VDC, since the bridge rectifier is mounted on the side of the enclosure for cooling.

    Maybe I update the PCB with bridge rectifier sitting on the PCB. You can see the bridge rectifier sitting at the bottom of this picture and the DC output wires from it goes to the connector: https://kaizerpowerelectronics.dk/wp-content/gallery/2009_07_22_-_Kaizer_SSTC_III/IMG_2437.jpg

    Kind regards

  62. Hey Mads!
    I would like to ask for your help! I built the tesla coil, and i have a problem. When the 30V test battery works perfectly, but when I add the 230V then after a few seconds of operation the Q1 mosfet breaks down. Thank you in advance for your reply!

  63. Hi balazs

    Its best to use a variac to bring up the voltage slowly.

    Try a lower voltage, like 200VAC. The antenna feedback can be very sensitive at full voltage and get disturbed by the powerful EMI.

    Kind regards

  64. hi mads ..
    I have posted the second one on highvoltageforum ..
    the first one is the slayer exciter and the second one which I include the picture below …
    i use a 275v 1uf capacitor to gate to gdt ..
    what is the range of voltage that can be used ..?
    so that the capacitor is not physically large ..
    Is it enough for the 1uf range between 25v to 50v ..?
    and is it safe to connect the secondary directly to the gate driver ..?
    I try to use an antenna it always fails to oscillate ..

  65. Hi men, i’m wanting to build one off those but i have a problem because i can’t find the ucc37321 and i wonder if i culd use the ucc37322 on it’s place, i was seeng other schematics and both mosfet driveres were ucc37322, but in others like yours with was based in stevs’s you used the ucc37322 and ucc37321. I relly wold love to know if it wold be possible tu use ucc37322 on both mosfet drivers. I would love a reply from a guy like you witch understand more from electronics , thanks.

  66. Hi Max

    You need to invert one input to one of the driver ICs then. You properly have a spare 74HC14 gate that can be used for that.

    Kind regards


    Look for a driver IC that has 5-9A peak output power and most important, to not make other changes to the circuit, a enable input pin.

    Kind regards

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