This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100 turns of 26 or 28 wire in a 1 inch PVC pipe. The antenna must be a long wire.
This is the traditional configuration of a 6 or 12 V source with 7806 or 7812 integrated circuits, for a...
This fader or guitar fading circuit was found in an American documentation from the 1980s. The...
Found in documentation from the 1960s, this power supply employs germanium diodes from the time....