Andrew Gabriel wrote:

In article ,
(A.Lee) writes:
So, an electronic ballast has a rating, as well as, in some cases a lamp
type. OK, thats simple. But then, there are so many lamp types and
wattages, that keeping a stock of ballasts in the van for each type of
lamp would be costly.
Testing a few yesterday, it seems they cannot be reliably inter-changed
between types.

A filament lamp is designed to run at a partcular power rating
when connected to specific voltage, and this is governed by its
operating resistance. To run it at the designed power rating,
you feed it a constant voltage, and it will decide what current
it's going to draw.

snip. Cheers, confirming my experimentation that swapping around the
cheap ones supplied with light fittings is a waste of time, and I need
to buy the correct ones.
Ta
Alan.

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