Good source of 400V electrolytics for stuffing

[Nick]

The question of ripple rating is always something that's concerned me,

Ripple rating is directly related to low ESR. Low ESR small caps are around, but the original caps in these radios were pretty rubbish - modern expectation of "low ESR" are in the low 10s of milli-ohms range... so I suspect that any decent modern capacitor from a reputable manufacturer will be better than that originally installed and a fraction of the size... Remember, V=I*R where V is the ripple voltage and R is the capacitor's ESR.

A REALLY simple trick to get lower ESR at a cheap price, if you have the room, is to simple parallel up a couple of capacitors of half the value you want. e.g. If you want a 16uF 400V capacitor, use 2 x 8uF in parallel (if they'll fit in the can) - you'll get half the ESR at a cheaper price. Of course, you can put any number in parallel to lower the effective ESR accordingly...

Low ESR HV caps can be VERY expensive. I have boxes of ex-equipment-but-unused 2200uF & 3300uF 450V ultra-low ESR caps (10-15mOhms) left over from a project (several other values too) - they are BEASTS (weigh 1.4kg each!) - Farnell & RS have them at over £90 a pop - Going on an auction site RSN (real soon now) as I need the space...