>But would they still blow on turn-on ? Quite happy with a 60W spot
>and it's not too hot. Just fed up replacing the damn things

The high efficiency bulbs are actually a fluorescent lamp of some sort with
either a small choke or electronic ballast. The latter are the higher efficiency
units. As I understand it the electronic ballast is done as a switch mode power
supply, so the lamp is driven with high frequency and you do not get the flicker
sometimes associated with fluorescent lamps.

The ones with a choke in them are a lower efficiency then the electronic ones as
the ballast generates some heat.

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