Gottlieb System 3 12v Power is located on the inside of the cabinet near the coin door to the right side. You will be looking for a 6 pin connector with a white wire on the end. Our products will use a 6 pin connector that has 2 wires attached to it.
Our power connector might look like this, which is our gottlieb to stern power adapter.
The black wire on our 6 pin adapter lines up with the white wire in the gottlieb power adapter.