Feb 19, 2013


Similar to the two transistor solid state Tesla Coil already on this site, this solid state Tesla Coil design uses a normal flyback transformer to generate it's high voltage output. Unlike the other circuit, this one does not use two huge power transistors and high wattage resistors. Instead it uses a 555 timer to more efficiently drive a single MOSFET. It's waveform has adjustable off and on time, making for an efficient circuit with little waste heat. It can be adjusted to drive most commonly found flyback transformers and can operate from a 12V to 18V supply. HV output can reach 60KV or more depending on the transformer and supply voltage. 



Total Qty.
R1, R5, R93180 Ohm 1/4W Resistor
R2110K Pot
R3, R7210 Ohm 1/4W Resistor
R415K Pot
R617.5K 1/4W Resistor
R81150 Ohm 1/4W Resistor
R1011 Ohm 5W Resistor
C110.0047uF 50V Polyester Capacitor
C210.05uF 50V Polyester Capacitor
C31220uF 25V Electrolytic Capacitor
C410.01uF 1200V Polyester Capacitor
Q1, Q222N2222 NPN Transistor2N3904
U11555 Timer Integrated Circuit
U21LM7809 9V Linear Regulator
L11100uH Choke Coil
T11Penn-Tran 1-017-5372 Flyback TransformerSee Notes
MISC1Board, Wire, Case, Socket for U1, Heatsink For Q3, Output Terminal (See Notes)


  1. T1 as specified in the parts list is going to be almost impossible to find, but don't worry. Penn-Tran was bought by Wiltron and no longer exists. However, most any medium to large flyback transformer will work as long as it does not have an internal rectifier. Suitable units are most often found in TVs made during the 1970s and 1980s. Look for the most impressive, dangerous, menacing transformer you can find. If you need an idea, a picture of a great transformer for use in this circuit:
    Nice flyback tranformer for HV circuit use
    These can be found in a small metal box generally in the corner of the TV case, complete with a very handy voltage multiplier unit and usually a nice heatsink.
    You will need to either look up the datasheet for the transformer you have, or probe it with an ohmmeter to identify the coil connections. Most flybacks have a load of taps on the HV side to provide focusing, horizontal and vertical signals. These taps are generally of no use to you. To find the primary (coil B-A on the schematic) you need to find the two lowest resistance connections that are not also connected to the HV secondary wiring. Alternately, if your flyback has an open frame like the one in the picture, you can wind on 5 or so turns of 16 gauge magnet wire as a primary. You will need to experiment with the number of turns to get maximum output. The HV ground lead (connection C on the schematic) is generally easy to locate. It will come from the HV secondary and be tied to the frame of the transformer or chassis ground.
    If by some miracle you were able to locate the Penn-Tran transformer, then connection B is the red dot on the transformer, A corresponds to the black dot, and C matches the orange dot.
  2. If the TV you salvaged the transformer from has a voltage multiplier unit (visible slightly at the far right of the above picture), then take it as well. It can multiply the output of this circuit into very high (over 100KV) DC voltages.
  3. When building the circuit, leave the flyback disconnected. Connect a 10 Ohm 10W resistor in place of the primary of T1 and connect a scope to the collector of Q3. Adjust R4 to produce an off time of about 10 microseconds. Adjust R2 for an on time of about 70 microseconds. Now remove the scope, 10 ohm resistor, and connect up T1. Power the circuit back on and you should have a high voltage available at the output. If you do not have a scope, just set both pots in their middle position and then adjust them by trail and error until you get the biggest spark at the output of T1.
  4. Q3 will require a heatsink.
  5. Needless to say, this circuit can produce dangerous voltage. At the very least you are looking at a painful shock. More then likely a decent burn will result from contact with the HV output, as well as instant and uncontrollable muscle contraction. If you have heart problems, don't build this circuit. Be careful!.

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