I have had this modification on my Getway for almost a year now. Its a great addition to the game, and it's fun to see the faces on people when they ask "does it really work with the game?".
Below is a circuit that worked for me, and a quick explanation of how it works. I am sure there are a bunch of ways to do it, but I found that this one was the easiest and I had most of the parts laying around already, so it was really cheap to build. If you end up building this project, send me a photo! It's not a complex circuit to build and I ask that you take the appropraite precautions when constructing this board. Remember you are building a board tha uses AC to power the light bulb lamps and the DC from the pinball machine to drive them. I recommend keeping the AC on one side and the DC on the opposite as to avoid any confusion when building this circuit.
And now the boring legal stuff.. . .
This circuit is provided "as is" and makes no representations or warranties of any kind regarding it. I disclaim all liability of any kind whatsoever arising out of your use of or inability to use this schematic. Ok, enough with all this legal stuff now onto the schematic! If you have any comments or suggestions, feel free to send me an email at email@example.com.
1 AC plug
1 small project box
3 MOC3010 optoisolators
3 6a 300v triacs
3 220 ohm 1/2 watt resistors
3 1k ohm 1/4 watt resistors
3 1n4001 diodes
3 47uF 10 Volt Electrolytic Caps
3 6 pin sockets (optional. It makes it easier to swap out an optoisolator if you mess up.)
Some wire and a couple of mulax connectors in order to split the signal between the full size stop light and the mini stop light on the playfield.
These components can be found at:
www.mouser.com (mouser electonics)
www.radioshack.com (radio shack)
(Click on schematic for a larger view)
It's actually a fairly simple circuit to build. The design uses 3 opto isolators(MOC3010) that drive three 6 amp triacs to turn the individual stop lights off and on. The opto isolators isolate the pinball machines DC voltage from the traffic lights AC voltage. Instead of the pinball machine driving the stop light directly, it drives an LED inside the opto isolator. When this led is on, it emits a signal to an internal led receiver inside the opto isolator and allows current to flow through the AC side. This current is what triggers the TRIAC to switch on and power the 45 watt bulbs in the stop light. The resisitors are there to limit the current going into the optoisolator and the capacitor is there to smooth out the DC from the pinball machine. It took some time to figure out the value for the capacitor. If it was too small, the DC was not smooth enough and caused the lights to flicker, on the other hand, if the capacitance was too big, the stop lights stayed on when they should have been flashing.
This part is up to you. I found that putting all of the Triacs on one side of the board made it alot easier. I was able to tie all of the ground lines together and then I only had to worry about the output to the stop lights. I also would recommend putting the Opto Isolators in sockets if possible. This way if you blow one up (I did when I first attempted to build this project.) you can easily swap out the optoisolator with a new one without having to desolder and all that fun stuff.
I chose not to install the board inside the machine and installed my board inside of a small project box that I mounted on the back of the stop light as seen here. I used wire nuts to connect the three lamps inside to the wires coming out of the bread board along with a common wire as well. This common wire attached to a small rotory switch on the outside of the box. The other wire runs to the inside of the pinball machine, through one of the small air holes on the bottom of the game. At this end I disconnected the mini playfield stop light and plugged it's cable into the splitter. I then took one end of the splitter back up to the mini stop light and then the other end is what hooked up to the large stop light.
(Notice, that similar to the schematic, I kept the AC on one side of the board and the DC on the other. The bottom of the board has all the inputs coming from the pinball machine and then the top of the board has the three wires that control the 45 watt bulbs in the traffic light.
Based on some photos he sent, it looks like the pinouts are the same in HS1 as well as HS2. So this mod should work fine for HS1 as well.