NOTE: I have the transistor backwards in this video! For some reason it still works with this particular transistor, but it won't work backwards with 2n2222a. You must connect Cathode of LED to Emitter of transistor and to B-. The Anode of LED goes to Collector of transistor and one end of coil. Thank you to acmefixer1 for catching my error....
People seem to be having trouble making the circuit using the "Secret Tech of the Pre-SSorbonites" video where I just show the thing without talking or explaining. I've even been accused of using two batteries or even faking!
I really get a laugh out of that one.... the fake stuff like the "coil antenna" debunk replication, people think is real, and the real stuff like the Joule Thief or electrostatic antigravity or wireless power ... people think is fake!
So here, I made another one just now, out of scraps on the workbench... and it works! This one is not as efficient as some I've seen, the scope shows that it has a fairly long on-time, which wastes power. But it does make nice oscillations and will run down to a battery voltage of 0.5 volts, about.
When I say the toroid is "magnetic" I mean it's attracted by magnets. It isn't itself a hard magnet.
I also tried a UV LED and a 2n2222a transistor. Both work fine-- when you have the transistor in properly. The circuit without the LED also oscillates nicely and makes 10 V peaks across the transistor.