Ok so we are making a tesla coil. Here is the circuit diagram we are referring: enter image description here

Now it worked when we first made this. The light bulb lights bulb when we bring it near to secondary coil. Then we decided to upgrade it to get some sparks. So we made some changes. The 2N222 transistor was heating a lot so we used the TIP31C transistor along with a heat sink (TIP31C is a power transistor). Now the circuit isn't working. We are getting a 700V reading at the base of the secondary so that means current is being induced but 0V at the top of the secondary which is quite strange. Also we checked the continuity from base to top and yeah the circuit is contiuous so now we can't understand where the voltage is being leaked. Please help out!

The setup if that might help: enter image description here

  • \$\begingroup\$ You will need 1kV/mm gap and V= LdI/dt so reducing dt turn off time or increasing I or L both increase V output. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 31 '19 at 17:43
  • \$\begingroup\$ You're missing a reverse-biased diode between the base and ground. This diode is necessary to ensure that the transistor shuts off completely. Also make sure you have the correct pinout for the TIP31C \$\endgroup\$ – DerStrom8 Apr 1 '19 at 12:28

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