Thanks gents
SSB receive is good. Seems to be very well on frequency, received audio is good, sensitivity seems pretty decent. I did the BFO alignment using the tool, and it came out about as expected.
But I think you've hit upon part (or all?) of the issue. I get no voltage at all to the mic. Zilch, nada, dead as a doornail. I did re-check the wiring, and there's nothing that I can see that looks amiss. I'll look at the diagrams again and see if I can figure out where that voltage is supposed to be coming from.
Tim