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[Yamamaya42]

From what I can see, there is no reason that Bob's design for the ballast should not be working, IF, it was made correctly, and there is no fault elsewhere.

You should take a very close look at it and how it was built.

This is my understanding of how it works.
CL-90 thermistor (120 cold 3 hot) = inrush dampening.
1n5408 x2 = dc for filament strings, lowers voltage & current.
39 ohms 7w & 18 ohms 3w = load balance for the 2 filament strings.
22-33 ohms 5w = shock dampening for voltage doubler capacitors / diodes.
200 ohms 5w = part of voltage divider for lower bias area.

If you go over it very carefully, and find no mistake, like something wired wrong, or damaged diode, or whatever, if it is getting too hot, then what part of it is getting hot?
What ever individual component that seems to be getting much hotter than any others, should be some clue of the problem.