Got a version 3 data east cpu board that I'm trying to troubleshoot. It was working fine until last winter, when suddenly it decided many switched solonoids should be activated all the time. I put it aside until our slow time, which is now. I've replaced the related transistors, 12 a and b, and 11 c, and gotten nowhere. While there are two PIAs apparently associated with the switch solonoids, I'd like to understand what I should be measuring before I replace them. For example, why is pin 12 of 11c high? I can see that pin 13 is connected to the 5 volts, so it makes sense that it's high. But, well, if it makes pin 12 high, how does that not end up firing switch solonoid 1 all the time?