I have an electronic device with a power supply board based on act4065a buck converter ic that steps down 12v of an ac/dc adapter to 5v to supply the circuits but it doesnt startup unless I touch the leg of some of the smd capacitors or resistors around the buck ic with any metallic tool such as screwdriver or tweezer. What should be the problem and how to fix it please?

 

Based on that description it seems that the power supply device is defective, if that is the one that requires a touch to start. I suggest trying it with a different 5 volt supply.

 

I have an electronic device with a power supply board based on act4065a buck converter ic that steps down 12v of an ac/dc adapter to 5v to supply the circuits but it doesnt startup unless I touch the leg of some of the smd capacitors or resistors around the buck ic with any metallic tool such as screwdriver or tweezer. What should be the problem and how to fix it please?

Probably a bad connection.

 

Certainly one simple option is to re-solder all of the connections. Much easier and faster thamn finding which one has failed.