Abstract: A power source terminal assembly for the wiring of electronic instruments, in which a plurality of terminal screw rods, each having a central flange, are molded into an insulating substrate with the flanges partly embedded therein. At least one of the terminal screw rods is designed so that one side of the flange projects outwardly from the substrate surface by a predetermined amount, and this terminal screw rod is used as a grounding terminal. A casing of an electronic instrument has a hole, for receiving the grounding terminal screw rod to permit one side of its flange to make contact with the casing, and a window for insertion of the other terminal screw rods without making contact with the casing. The power source terminal assembly is engaged with the casing, and the grounding terminal and one portion of the power source assembly are fixedly retained by fixing means to the casing.