I received a Google Alert which linked to this Youtube video which consisted of about a minute of nothing else but a schematic of a circuit, with a lot of background noise. The circuit consisted of a single transistor with a coil, capacitor and 68 ohm resistor, and of course the LED. I tack soldered the circuit together with the same components, except for the 100 uH choke, which I instead used a 180 uH choke. The transistor is labeled 2N2222, which comes in a metal package, but the picture showed a plastic package, which is actually a PN2222A or MPS2222A.
I set the supply at 1.5V and the LED lit up but not very brightly. The current was about 12 milliamps. I measured the voltage drop across the 68 ohm resistor; it measured 0.8V, more than half the supply voltage. Since the whole supply current goes through this resistor, over half of the power is wasted in this resistor. This makes for a very inefficient Joule Thief.
The frequency meter measured an extremely high 700 kHz, in the middle of the AM broadcast band. This is a bad place to be since it interferes with the radio stations. I have a strong suspicion that since the circuit includes a choke and capacitor, it actually is oscillating as a tuned circuit, not a true Joule Thief where the coil alone is producing a back EMF to light the LED. I cannot confirm this because I still have not found the box where I packed my digital oscilloscope when I moved. I haven’t even fired up the windoze PC that it was connected to. I opened up some more boxes this weekend so I’ll eventually get to it. I would assume that if the 180 uH choke was changed to the 100 uH, the frequency would be even closer to the middle of the AM BC band.