They are connecting to pin 3 of the 7805 voltage regulator. That is the +5 in the schematic. They are also using pin 2 of the regulator for ground but you can use any ground point on the PCB. I'm having trouble finding a pinout of your transistor to really help you further. That video amplifier schematic almost seems too simple and I would think that the transistor you use would make a difference. I don't know...maybe it works just fine.

Also, if the Famicom stopped working then my guess is that you shorted out the regulator.