The circuit shown is for testing both signal diodes (low current) and rectifiers (high current). The circuit is from a 2000 Poptronics, and the transformer has a secondary winding of 100 to 300 mA.
This conventional bistable power control circuit using triac was found in the June 1970 Radio...
In the figure we have the circuit of a multi-range ammeter using a 50 uA full-scale instrument. The...
In this radio the coil can be made with 70 + 30 turns of wire 28 to 32 in a cardboard or PVC tube...