9V power source (CB21164E)

This simple circuit with a 5V regulator was found in an American documentation from the 90's. The output voltage is adjusted in a trimpot.

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Capacitance meter (CB22163E)
Found in an English documentation from 1989, this circuit uses components common today. The...
Simple capacitor test (CB7060E)
The LED frequency flashes depends on the value of the capacitor tested according to the table. We...
Hartley crystal oscillator (CB7541E)
Found in a Popular Electronics from the 90s, this circuit generates a signal that depends on the...