The transformer inf this circuit is a 6 or 9 V unit and diodes 1N4002. The filter capacitor is 2 200 uF and R1 of 1 k ohms wire adjusts the output voltage. R2 is 1k and the instrument is a milliammeter that must be adjusted in terms of voltage. You can use the multimeter to adjust the voltage. The current of the transformer can be 100 mA or greater.
