[Arran]

Codefox, I'm keeping the same capacitance the sets were designed for, I just wondered if my 400v caps that were at their upper voltage limit. I don't have an issue with the slightly higher price of the 630volt caps, I just happened to get some 400v units at the time. I'm trying to stay away from electrolytics whenever possible when I rebuild a unit, that's why I'm using plastic caps whenever possible. FWIW, I found 600v plastic caps at AES. B+ shouldn't be an issue after replacing the filter with the same capacitance.
Music, my 20 lists a primary of 105-125volts. However at 125 the secondaries will put out a higher voltage than the tube filaments and plates were designed for. Recent threads on ARF discussed using a bucking transformer or a resistor in series with the primary. The obvious issues are finding space for a transformer or adequate area for heatsinking a wirewound resistor. I have a Japanese superhet with a 100v primary I run off a variac as I haven't gotten around to reducing the input voltage permanently.
Dave

In my experience 400 volt condensers are usually fine in most old radios, I have a number of .047 mf 400 volt ones that I have used and none have failed. The typical plate voltage in an AC set isn't any more then 275 volts running, and maybe 350 volts on start up, most circuits will not see anywhere near that. One area where I would use a 630 volt unit is a situation where if the condenser fails that the B+ would short out of find a low resistance path to ground, some tone control circuits could have this happen. Electrolytics will work fine in place of a large paper condenser, just make sure that you get one of the right voltage and observe the polarity correctly.
For the Japanese radio I would take a look at junked printers, scanners, and other assorted consumer electronics for a bucking transformer, some were 25 or more volts at a high amperage, I would then build it into a box with a standard electrical outlet with the transformer in series with one side of the line.
Best Regards
Arran