I know this post is 3 years old but It helped me tremendously thanks to kbliznick and hopefully someone who needs help will read this one day. I had a similar issue with my SST. Lamp matrix column was out including segments, solenoids were out, and stepper motor was not working right. Wierd thing was everything that was out was on pin4 of its connector. Turned out it was address D2. The ribbon cable on CN1 from the CPU to the driver board has an intermittent open and if I moved it up everything comes on. All this happened when I was reseating cables and socketed IC's because the game was running real slow during boot and between balls. I switched to NVRAM which resolved that issue.