The foreign 50hz stuff I've seen is a lot more massive than
my home grown 60hz equipment. I've worked on all sorts of
switching power supplies but I've never seen a 1Mhz unit.
Is it something that would be an aerospace/military item?
Thats why Westinghouse beat Edison in the early days of deciding what
electical distribution system to use, Westinghouse (scientist) wanted
AC, Edison (who was more of an inventor than a scientist) would not
let go of his prejudice for DC. I still have an old AC/DC radio from
those days, when radios were sold to work on either distribution
Westinghouse was an inventor, and entrepreneur (as was Edison) - who
recognized good ideas when he saw them and a way to get around Edison's
stranglehold on the electrical "lighting" systems. This was weakened before
Tesla, by Gaulard and Gibbs who invented the transformer (1886 or
thereabouts for the first AC transmission). - making long distance
transmission possible. polyphase machines invented by Tesla were the icing
on the cake, and 3 phase systems followed soon after. Edison wanted to hang
onto his empire- so fought tooth and nail against AC- he had a good thing
going. Tesla once worked for him but got shafted.
As for the radio- If I recall correctly, until the late 1920's all radios
were battery powered. Then AC/DC units came into use. Better ones used
transformers to get the various voltages, filament and plate (replacing the
old A and B batteries).
The typical smaller radios that were sold in the 40's and 50's would work
on DC as they did not have a transformer, and tubes operated on the
rectified line voltage, with tube filaments in series. This was done, not
with intent to use them on DC supplies but because they were considerably
cheaper to build but could have a hot chassis (safety? what's that?).
The history of those times is very interesting. An often ignored inventor
who thought things out before trying them (as opposed to the Edison
approach) , was Elihu Thompson.
When I was a kid, I got hold of an old tube type record player
that had a metal chassis, for some reason when I was playing
around with it on the back porch of our house, I got lit up.
DANG!! This was long before two wire cords had a wide bladed
neutral. With all the electrical devices I played with when
I was a kid, I'm surprised I ever survived.
On Fri, 09 Oct 2009 18:49:52 -0500, The Daring Dufas
Somehow my hand ended up between the poles of a 10kV Jacob's ladder on
day, while sitting indian style in front of it.
It shot me back about seven feet (my legs). I am sure I clamped the
supply down to near nothing, since it was only a 10mA furnace ignition
That one was phase independent. Surprised I survived my youth as well.
I made a shock box "lie detector" as a science project, and was
shocking parents with it... mostly. Back then, a kid could get away
with that stuff.
I've been told that when I was an infant crawling around the house
back in the middle of the last century, I unplugged the power cord
from the bottom of my mother's Singer sewing machine. The other end
of the cord was still plugged into the wall outlet and being the
curious little brat that I was, decided to determine what a power
cord tasted like. I've been told that I turned blue and my diaper
had to be changed. Ever since then I've been getting in trouble for
things I've done with electricity. When I was a bit older, I would
build Frankenstein like machines in the basement and being no fool,
I would get one of my little brothers to plug it in while I took
cover behind something. It made my butt hurt for some reason.
AC/DC radios were born out of the great depression. It was the
Volkswagen Beetle of radios. The reason for the design was that it
eliminated the (expensive) power transformer by wiring all the tube
heaters in series and made the set much cheaper to manufacture. A useful
side effect of this was that it would work on either AC or DC. An
additional potentially very dangerous side effect is that depending on
which way the plug was inserted into the receptacle, the entire metal
chassis could be live, including shafts that would be exposed by a
The classic "All American Five" so named for the lineup of five tubes
used in virtually all of them was prolific up into at least the mid 60s.
It really is remarkable just how well it worked, despite circuit layout
and wiring techniques that would make an RF engineer cringe. It is
highly advisable to power these from an isolation transformer.
Incidentally, I read a few years back that it wasn't until the late
1990s that the last DC service was disconnected from a building,
somewhere in NY I think. I was amazed by how long it remained in use.
Servicing some legacy elevator motors or building water pumps, IIRC.
Wikipedia has a pretty good writeup, linked from the 'current wars'
articles. Isn't their subway system still DC? I would never want to live
in NYC (or any huge city), but I do find the historical stuff about
their physical infrastructure quite fascinating. The occasional show on
History, Discovery, or similar channels always sets me off on an
internet hunt. If I could get shows like that on over-the-air TV (like
PBS in the old days), I'd probably get rid of my satt service.
On Sat, 10 Oct 2009 10:27:26 -0700, Archimedes' Lever
AlwaysWrong strikes again.
Definition 2a: preconceived judgment or opinion
It has a negative connotation because it is preconceived, not because
what is preconceived is negative (or even AC).
On Sun, 04 Oct 2009 22:11:23 -0500, The Daring Dufas wrote:
Around 2002 I found a wonderful mid-sized mercury arc recifier
in use still for the tram system at the MOTAT museum in Auckland, NZ - it
might still be operational there. Fascinating to watch it run, and the
brightness change according to load as the trams moved around.
I'm sure there are still some running in other countries, too, but that's
the only one I've seen over the years (although various museums have ones
that aren't hooked up - I don't know how many of those are still
technically OK and could be made to run).
There may still be a few tucked away in buildings with really old DC
elevators, although there can't be many left now that haven't been
On Sat, 10 Oct 2009 15:56:02 -0700, Archimedes' Lever
You really are a dim bulb, DimBulb. You said: "I do not think there
have been DC elevators in the US since the late Thirties". The fact
is that there _have_been_ (i.e. existed) DC elevators as recently as
2007. In fact they are likely still there, though the conversion
would now be done on-premises.
In short, AlwaysWrong, you're wrong again.
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