Leak Detector (CB22456E)

We found this circuit in a Popular Electronics from 1992. The transistor is general purpose, assuming equivalent.

Turntable Preamplifier (CB19172E)
This RIAA equalizer preamp was found in a 1990s schematic. The transistors are an old version of...
Battery Status Indicator (CB15852E)
This circuit uses two LEDs to indicate the state of a battery, the voltages at which they...
AC Motor Control (CB12330E)
The bridge diodes of this circuit, found in a 1967 publication, are according to the motor...