The Stern Shaker motor per their schematic operates on 24 volts AC. It comes with a circuit board that has some beefy diodes and a resistor along with 2 fuses and 2 plugs. The circuit board rectifies the AC voltage to DC current and the resistor makes it closer to a usable 12 volts as the motor is rated as such. The board has 2 plugs. 1 plug(2 conductors) to the motor and another plug also 2 conductors for power and trigger (ground). I initially tried to run the motor on a separate small 12 volt power supply since there was no 24 volt AC available in the game but the amperage was not enough.
Further research found 20 volts AC directly from the WPC transformer to the sound board so I figured a 4 volt difference couldn't be that bad and I tapped this supply line near the J501 header plug with the red power wire from the shaker board.
Looking again at the stern schematic the other wire (brown), is instructed to plug into some specific under playfield harness but to complete the circuit it appeared to simply need a ground to activate. I tested it on a ground braid and that thing shook like a beast!! However I chose not to connect this wire to any direct sources in my game but instead chose to ground it through a relay to prevent any type of electrical surges or short circuits.
The next deli-ma was that I knew I wanted the shaker to activate with the time expander. My relay will trigger from a + or - source but not both..it is selectable. So I figured I would tap into the time expander motor power wires and use this to trigger the relay to trigger the shaker right??? Wrong...the time expander motor reverses depending on game play so either wire will potentially have + and - currents at any time which means the shaker would only work half the time the expander is moving. I suppose I could have used diodes to block the reversing current but I did not want to risk damaging the bi-directional motor board. Those things are sensitive and I already damaged it early into my restore while rebuilding my time expander.
Better solution...Looking at the Williams schematic for the Bi-directional motor driver board I noticed one circuit determines the direction of the motor and another circuit simply turns on that circuit or opens the gate for it to function. Tapping into the circuit that turns the whole system on was perfect for my application. This wire plugged into J122 header on the main power driver board. I tapped it there and found it needed a diode to correctly operate as it carried power but switched to ground during function.
That's basically it!! Functions perfectly...As far as power requirements the 20 volt AC from the transformer is plenty enough for the stern board. The tricky part is integrating the trigger source in other games. When do you want it to shake and what will activate it? it is very possible to make it work however you want using standard relays and adjustable time delay relays. The PIG adapter may help in this area also. I recommend the ELK brand relays as they are solid and very functional. http://www.at-fairfax.com/ConstructionElectronics.htm
Im not an expert but I might be able to help if anyone has specific questions.