Another wrinkle:
After pulling the tube out of the socket. I still measure a dead short to ground from the plate side of the 100K resistor. I lifted that side of the resistor, so now I'm essentially measuring the continuity of that trace on the PCB. Sure enough, dead short. I start following it down the PCB and removing components along the way. The only other one I come to is the 2u2 cap just before the output transformer. When I lift the side connected to the same trace as the 100K, I check the continuity again. This time I show no short. I put the 100K back and measure the plate connection against ground. No more short.
Now I'm looking at the capacitor. Measuring the side of the cap that connects to the transformer, I get a short to ground.........
HOLD EVERYTHING!!!!
I FOUND THE PROBLEM!
While I had the transformer end of the capacitor unattached, I again measured continuity. No short. I then barely touched the loose capacitor lead to the PCB and suddenly saw the result I was after. So what went wrong???
Turns out, the lead was sticking through the hole in the PCB, just as one might expect. I had snipped it off right at the surface of the other side. However, there was still a tiny little tip of a lead poking out. And what, pray tell, was that touching???
The shield can of the output transformer!
After laughing my head off and calling myself everything but a gentleman, I promptly resoldered the cap to the trace side of the PCB, keeping it well away from the shield can.
I powered it up and checked the plate voltage. SUCCESS!
I put the body back on and connected it to the mixer and put on the headphones. There was my voice, in glorious in-your-face tubeness!
And did I mention that this mother is QUIET!!
I thank you all immensely for your time. I raise a frothing pint in your general direction. Please accept my profuse apologies for bringing you all this way for such a simple thing. And finally, to Jakob and the crew at Gyraf...
TAK!