[Arran]

With replacing a selenium in a portable you do need something to drop the voltage, in other sets where the selenium was strictly for B+ I sometimes never bothered with the dropping resistor, the tubes usually drag the B+ down far enough and the seleniums were already instant on so the circuitry was designed around this. With regards to the size of the filter condensers there seems to be a law of diminishing returns in terms of larger capacities boosting voltage, going from a 2mf to a 4mf causes a boost, as does going from a 4mf to an 8mf, but when they get larger 8mf, 10mf, etc it doesn't seem to matter so much. I have an AC5 (Canadian AC/DC) which has a pair of 160mf filter condensers in place of 40 or 50mf ones, the B+ is dead on to where it should be, according to the schematic.
Best Regards
Arran