I think they intended to place a junction dot just above the 220uF capacitor but the circuit is very poorly designed. It has no feedback to regulate the output and the current limiter is somewhat doubtful in operation. Under the right (or wrong!) circumstances it could simply burn out the voltage control potentiometer. I have doubts it could produce 30V at 2A load without considerable ripple on the output voltage too and the rectifiers would be run at double their rated current.
Brian.