[Yamamaya42]

It's not unheard of for a FBT to develop poor solder connections from the windings to the solder pins themselves.

Once it starts, it begins a downward spiral due to heat and carbonization.
And from what I understand the FBT does run hot in this.

But if this is the case, it should be easy to fix if one is careful, because there is normally enough healthy winding to re-solder to.
But the FBT has to be removed and looked at closely like under a microscope to see if this is what is going on.

Also, RCA seems to have done things extra weirdly in this set, unlike in the roundies I have seen before, or even the CTC-38, which had a conventional damper tube and Shunt regulator, unlike the SS damper in this and pulse regulator.

The pulse regulator may be a source of trouble, but I doubt it can kill HV completely, from what I can tell, it comes into play after the FBT has been excited and started up, and in this case, it's not getting to that point.

Another thing to look at aside from poor connections on the FBT are the resistors on the output PCB, perhaps some are bad or out of tol and not allowing it to ring up correctly.