This resistance meter was found in an English documentation from 1989. The operational amplifier admits an equivalent and the transistor can be a BC558 or BC559.
We found this simple transistor tester in a French publication in 1981. It uses a common analog...
This circuit was found in the September 1984 issue of Radio Electronics magazine. The circuit is...
We found this circuit in Ferranti's 1974 transistor manual. The components are from the period. Note...