Old School capacitors

4uF@1000V Oil filled capacitors for filter use from the 1930's. The capacitors are still perfectly good. In the old times, large filter chokes of 10 to 30 Henries were used as power supply filters. Electrolytic capacitors had not been commercialized at that time. The combination of a choke as the input element followed by a capacitor to GND still, to this day, provides better voltage regulation than a capacitor alone, even if that capacitor is hundreds of microfarads. Filter chokes are expensive. Choke-input power supply filters have been mostly disused in consumer and amateur high voltage equipment for reasons of profit, cheapness, weight reduction, or size reduction.

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