In the original circuit a 40431 quadrac is used, but this is not a common component today. Replacing it you can use any triac with any diac according the current drain of the load. The triac (or quadrac) must be mounted on a heatsink. R1 is a 3k3 ohm resistor if the AC power line is 110V or 4k7 ohm if the AC power line voltage is 220/240 V. R2 is a 220k or 250 k ohm potentiometer.
Power Control (Dimmer)
