This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent components. The transistors may be BC558 and the transformer is obtained from a disused transistor radio.
This circuit was found in a French magazine Toute LÉlectronique from 1978. Transistors are not...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
The resistors R1 and R2 consist of 8 220 ohms x 2 W resistors connected in parallel. The...