As posted previously, I'd built and mounted the C4S boards and was engaged in the driver testing when I believed I accidentally shorted either the IA or OA pad to a transistor leg with a VOM probe. This happened after getting good readings at IA and OA and then adjusting the trimpot to get a good reading at 46U. In other words, everything seemed fine, and then I made a slip in a recheck with catastrophic results (or so I thought). The 90.9 ohm resistor and two A-side LEDs exploded pretty dramatically. I built a new board, installed it and fired it up. As I sat waiting for the B-side LEDs to glow, the same thing happened again: the resistor and LEDs blew, without my having gone near it with a probe. Correlation was, apparently, not causation. Everything had passed muster through the high voltage power supply test, and starting from that point in the manual, I've reviewed all the connections and don't see what I am missing. But there must be something! Any suggestion (s) where to start would be much appreciated.
