I have made power regulator with pic16f84a. Everything works fine, while microcontroller DD1 supplies current to transistor VT1 base: VT2 is switching circuit VT2-Rap-VD1_VD4. Rap is load, in my case 100W incandescent lamp. If i remove PIC 16F84A supply (5 volts), but leave 220V supply to load, VT2 blows out in a moment and base-emiter junction becomes 0 ohms. Maybe there is a problem i VT1 and VT2 connection? Any ideas?

 

Your circuit is a lethal shock hazard. You remove the protection of the step down transformer by strapping the 5 volt ground to the AC line.

VT2 should be a triac, and be triggered by an optoisolator. It's simply too dangerous to use as it is.

 

Wow, that is certainly scary!