P-Series Valves, what to do with them?

[ppppenguin]

At least we've cleared up the mysteries. It certainly wasn't obvious to me why a cap should give lower surge current than a resistor and it's still not intuitive why this should be so. The calculations prove the point but that's different from instinct. A diode dropper won't reduce the surge current, in fact it makes matter worse. I've just crunched the numbers for Trevor's example. As it happens a diode gives almost exactly the right amount of drop with no extra resistance needed.

With a resistive dropper the surge is 727mA. With a diode it's the efective mains voltage (165V) divided by the cold resistance of 90R. Just over 1.8A. More than double!

That surprised me too. To try and reach an intuitive answer, the greater the fraction of the chain that has a low cold resistance, the worse the surge. I'll think twice before using a diode in the future.