Ok, just for a quick test, looking at the schematic ArthurDent posted, I simply connected the Variac between the red and black wires only (directly across one of the primaries on the transformer. I turned on the Variac and slowly brought up the power and sure enough, the unit powered up! No adverse effects as far as I could tell. So this suggests to me I could jumper the brown stub to the black wire as Ed & Arthur were suggesting and the unit should work as expected, no?
Thanks again guys for the continued support!
Cheers,
Matt