Just for informational purposes, if someone wanted to build a modern (by modern I mean 1970's and later) pinball they haven't changed much in basic functionality. There are 6 components that make up a pinball.
1. MPU - Brains of the pin, contains the ROM image with all the game logic.
2. Solenoid control board - Controls firing of the 10 or so coils in the playfield (pop bumpers, sling shots, drop targets, etc.)
3. Lamp matrix board - controls the lamps through a matrix configuration to limit the amount of IO lines required by the MPU
4. Power Supply - self explanitory, except you need multiple voltages, typical 12v, 5v for the logic boards and higher votlages (24 +) for the solenoids.
5. Switch Matrix - Again the input switches throughout the playfield that tell the MPU where the ball is, and again this is matrixed to conserve IO lines on the MPU
6. Playfield - this is were I believe the hardest part of building the pin is. At least getting it to work right and honestly getting the game flow to work correctly. You can't just throw stuff out there on the playfield with out some thought as to how fast or slow or technically challenging you want your game play to be.
I actually have most of this built or scavanged from my parts bin, I just need the time to start putting it together and I have yet to decide the best way to set up a temporary playfield to test the physics and game play, that allows me to move things around, yet will stand up to being hit by a 1 1/16" ball bearing.
I definately plan to take lots of pics and will put them up on my site for anyone interested, but I don't know when I'm actually going to be able to start it as I have just received a Gameplan Foxy Lady cocktail that needs some love.