Continuation of the Lanier Diaries here, decided to bring the Lanier up gently on the Variac to see if the lack of printer was the cause of it not booting.
Did so, net result was the printer smoking up and taking the +5V power rail with it. Possibly the root cause of the initial failure.
Took the Qume apart and cleaned it out. There were a few nuts and bolts rattling about inside on the circuit board. That might have been part of the reason also.
I shall henceforth be fitting fast-blow fuses to the 5V rail.