ok, i think i may understand it... hoping for clarification tho.
as we all know, inductors oppose change in current flow. and caps oppose changes in voltage. ya, ya, call me captain obvious, but bear with me... as the first diode charges C, the CT is also charging the inductor, as the power through the diode swings negative and the diode blocks, the second diode is swinging positive and charging the cap and the choke. the choke acts like a current pump for C during both 1/2 cycles or 120Hz. that's why the CT is placed between C and L. in other words, the center tap keeps L charged and L pumps current into C and as the V across C falls C needs more current to oppose change, so our inductor will discharge. it's ingenious, the vacuum diodes see a capacitive load and inductor is "hidden". you can use low values for C since the inductor acts like a current pump, the effective capacitance is larger.
it's ingenious if caps are expensive that is... however today, even 600V caps are much less costly than big iron, and caps weigh much less. even now 600V caps are getting harder to find, but we can series stack them and it's still much less moolah than big iron.
by the way buttery, the OT is fried - 1/2 primary is open. it came that way - i'll explain l8r.
sometimes, in darkness there is light...i think we may have found replacement iron for glo-champ. the 5V ran 2 x 5U4G - that's 6A. 4E27 takes 7A but i'd bet baldwin iron is overrated. this will liberate design of one more piece of iron. i'm going to have to recalculate B+ tho looks like it'll be closer to 600V, so glo champ will need new bias resistor - but then again, maybe not.