Yep. That's what it is - bad ground on the 390k resistor. I jumped it with a piece of wire and the set acts a LOT better. I can JUST get 23.5kv out of it, but the regulation is a bit poor. So I might have another issue in there (I'm recapping the sweep board anyway, so I'll check it tomorrow), but temp jumper helped out a LOT. The 6BK4 is glowing nicely, so I'm sure I'll glow in the dark tonight!
Horizontal current (untweaked) is about 195ma. I can get 23.5kv if I turn the HV adjust full up. Width is awesome
So, I'm getting there. I wonder how repairmen felt about RCA vs Zenith, in terms of serviceability - the Zenith just seems a cleaner design overall (I've got a 25LC20 coming up as the next contestant).