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Cydrome Leader

In sci.electronics.repair wrote:
On Wed, 27 Feb 2013 20:24:30 +0000 (UTC), Cydrome Leader
wrote:

In sci.electronics.repair Arfa Daily wrote:
Has anyone seen any good write-ups on, or figured out for themselves, just
how the self-oscillating dirty - i.e. smoothing cap-less - switchers that
you find in use as lamp ballasts (or 'electronic transformers' that they
seem to be sometimes known as) work ?

I recently acquired a fairly sophisticated disco lighting fixture that has
such a supply to run the 24v 150 watt lamp. It seems to have two main
switching devices, which I suspect are FETs or IGBTs, but can't tell for
sure so far, as the numbers have been ground off them. On the mains side,

That's pretty high tech for a product from the 1970s to use a switching
power supply.

They weren't all that unknown in the '70s. Almost all of the large
supplies we used were either switching or phase controlled (the really
large ones). I only remember one linear supply above 1kW, and that
was a 4V 1000A HP that was used in a piece of test equipment. Big as
a refrigerator, it was.

ha. that thing must have been about 12% efficient.

I saw some open frame "international" style linear power supply at a
surplus dealer marked Intel with the Intel logo that was rated tens of
amps at something like 1.8 or 2.2 volts.

It was one of those preposterious things with extruded heatsinks and the
bent aluminum chassis around all the TO-3 cans.

I've noticed "interntional" linear power supplies these days are complete
crap compared to the ones from yesteryear. Condor was still making
somewhat decent ones about 5 years ago complete with silkscreened
copyrights of 1990 on the PCB and case.