Many thanks for the insight, Andy. I had never come across an 82E149 card in a dual line configuration. These cards would appear to be mic/line cards, though, given the presence of D1-D4, the zener protection diodes for the mic input. In either configuration of the 82E149, caps C13-C16 are biased up with the 48 volt supply, and I still suspect those caps aren't 100 volt rated, leading to their untimely demise.