Continuity tester (CB7386E)

This circuit was found in a Hands-On Electronics from the 90's. The FET can be any general purpose.

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330 Degree Control with SCR (CB6565E)
Suggested by an American documentation for 1969 neon lamps, this circuit provides SCR control with...
Crystal Tester (CB13530E)
This circuit was obtained in a 1976 amateur radio manual. The circuit can be made with a 2N2222...
Preamp for millivoltmeter (CB21863E)
This circuit was taken from the 1974 Ferranti transistor manual. It is intended to use a common...