In article ,
Derek Geldard writes:
On Sun, 30 Sep 2007 07:23:08 GMT, Jason
wrote:
We had dimmable fluorescents in the lecture theatres at university, back in the
early 80s. It's not like it is a new technology,

In the '80s (potentially installed in the '70s) it would have been
done using a large saturable reactor, or maybe a large variac. I've
never seen one but potentially the size and weight of a volkswagon
beetle.

Transtar were making triac dimmable fluorescent ballasts
in the 1970's. They were the main manufacturer of dimmable
fluorescent control gear at the time. They provide a continuous
heating supply to the tube filaments. I rather wanted one
at the time but couldn't afford them, so I made my own.
Don Klipstein has captured an old usenet article I wrote
about designing my own on his web pages...
http://members.misty.com/don/f-dim.html

--
Andrew Gabriel
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