Here is my latest germanium Joule Thief, shown squeezing the last few hundred millivolts out of the Energizer Bunny (“It just keep going and going…”). This is a real Zombie Battery Killer – that last half volt left after the regular silicon JT has given up is now sucked out, down to less than0.2V. This one uses a General Electric 2N525, most likely made in the early 1960s. G.E. was a big manufacturer of semiconductors, but left to manufacture the appliances such as the Toaster Ovens and coffee makers we’re all too familiar with, and jet engines. I still have one of their gigantic copper oxide rectifier stacks which looks like a selenium rectifier stack only the plates are round, not square. And I have several thousand of the GE 2N5172 transistors, which are still available today from other manufacturers. The G.E. Transistor Manual, 7th Ed. (1967) was the bible for any engineer or tech working with solid state components. But today, most germanium parts are made by plants in eastern European countries and have been almost totally replaced by silicon in modern equipment.
I have been measuring the AA cells after they have been drained by the germanium Joule Thiefs, and the cells measure less than 200 millivolts, some as low as 150 mV. When disconnected, they will recover some voltage, but they are much more lifeless than when they were on a silicon Joule Thief.
Back to experimenting…