Let's see, I've done the misaligned cable once, that took an hour before my eyes caught it. I also replaced a EOL switch and flipper coil. I sodered the leads on the wrong terminals. So when I turned it on it cycled like crazy and died. I thought it took out an SCR. So I replaced the MPU and then power supply with spares. Turned out my EOL switch was just barely open instead of closed. It was the simple thing and not the Apocolypse. Lesson: No more wine during repairs, even simple ones.