Once you have completed the assembly of the main PC board (see Fig,3 last month), the metal contact screw can be installed as shown in Fig.7. This done, cover the exposed end of the contact screw, the nut and the surrounding PC board area with a generous coating of neutral-cure silicone sealant, so that there is no exposed metal on the component side of the PC board.

Smear the silicone sealant on with a wet spatula and make sure it adheres to the surface of the PC board. Apply a second coating if necessary.

The ends of the 4.7MΩ resistors should be cut off flush with the top surface of the PC board. These resistor ends and the surrounding board area should also be covered with silicone sealant, so that the mains cannot possibly directly short against them or the metal contact screw.