today I tried to make my own Tesla coil circuit according to the schematic below, except that I have changed the number of turns on the secondary and primary so could get a higher output voltage (1 to 500+ turns). That's what I was trying to do. But I have come across a problem. I used Power transistor (BD243C) instead of the 2222A. I wired up my circuit according to the schematic below with red LED, 9V battery but without switch to see if it's at least working.

The circuit doesn't work as expected. My LED didn't light up, transistor is heats up. There are voltage drops in the circuit which I probed but no sign of high voltage output. Can anyone notice something weird and tell me?

enter image description here

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Thanks to everyone who post a sensible and helpful answer.

  • \$\begingroup\$ 1. This is not a Tesla coil. 2. You probably need more then 1 turn in your primary for sufficient inductance to resonate at a low enough frequency for the transformer to switch. 3. Changing transistors could affect bias needed and make it not operational at all. 4. Shorten all your leads and heat sink the transistor. \$\endgroup\$ – MadHatter Jul 21 '19 at 18:01
  • \$\begingroup\$ @MadHatter, thanks for clarification it's not Tesla coil. I have scavenged this transistor I used from the old Tesla coil which had less turns. So I think transistor is good, no? \$\endgroup\$ – MerryGR Jul 21 '19 at 18:08
  • \$\begingroup\$ Have you tried swapping the leads going to your primary coil in case it's out of phase? \$\endgroup\$ – MadHatter Jul 21 '19 at 18:09
  • \$\begingroup\$ @MadHatter you mean the right lead should go to the resistors and the left lead to the collector of the transistor according to the picture I have taken? \$\endgroup\$ – MerryGR Jul 21 '19 at 18:13
  • \$\begingroup\$ Yes. If they are backwards, your feedback from the secondary will be 180* out of phase. \$\endgroup\$ – MadHatter Jul 21 '19 at 18:14

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