This ultra-simple 9 V power source was obtained in an Argentine publication of the 1970s, but it is a very common circuit in many other publications and practical applications. With 6.3 V rectification, the capacitor charges with a peak value of this voltage, which approaches 9 V. The power supply is unregulated and is suitable for loads up to a maximum of 50 mA. The transformer must be 6.3 V with a current of 50 to 100 mA. The capacitor can be from 250 uF to 1000 uF. With higher values the voltage will have lower ripple level.
