This simple indicator circuit was found in a documentation from the 90s. Trimpots can have values between 2k and 10k, a series resistor is recommended to limit the current to the minimum setting.
This circuit with SCR is from a Radio Electronics magazine from September 1965. It is a commercial...
This circuit was found in the July 1986 issue of Radio Electronics magazine. The circuit has a...
This circuit was found in a QST from the 1990s. The circuit expands the scale of a 10V instrument to...