Here's a closeup of the Studio II's RF modulator. The power supply also comes in through this cable and is separated here.

It is interesting to note that all the components attached to the circuit board are through-hole. Although surface-mount technology had existed since the '60s, it was still more expensive than the commonly available through-hole components of the day.

The pattern for the traces connecting components across the board is most definitely hand-drawn. This was very common before computer-aided design programs were used to make very straight, organized traces. Most of the wide solder areas are the ground plane.