The really big ones - Ignatrons (sp) used arc points and were the
10,000 amp class of SCR's. Still in use I suspect - plating plants....
Many power amp tubes of all sort used the stuff - I have some in the shop.
The internal arcing - getting the getter to activate and vaporize onto
the walls was done by an RF probe that injected through the glass
(acting like a cap). Many power rectifiers and power triodes (like two
fists on top of each other) had Hg in the current flow.
I might have one of those in the shop, but seems to me it was replaced
with solid state.
Heat in the normal tube wasn't enough to activate atom mobility.
It is a small point that is in a cup and then coats a small area of the glass.
Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
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Joe wrote:
On Sat, 20 Sep 2008 21:46:42 -0500, "Martin H. Eastburn"
wrote:
The silver looking stuff in Tubes is mercury.
The getter was a pan of mercury and it was excited by an RF probe after
the tube was sealed on the line to oxidize itself so when the filament
is heated to red to red-white in color it would last many hours.
I've made tubes that you could pass a lunch box through without touching
sides. The filament was as large as a pencil. It was a research tube.
The largest I have put my hand on was 15 feet tall. The smallest was just
larger than a pencil eraser.
I taught Tube design (circuit) and later, taught EE's who knew tubes
solid state. So I had to know both designs and show relationships.
Eimac was the maker of Power transmitting tubes. I think of pyramid tubes
and potato sized kilowatt transmitting rubes. TV and Radio as well as
military used them. I think I have one or two in the shop. They used
to advertise in ELECTRONICS magazine in the 50's. Those were the years.
Martin
Martin H. Eastburn
Mercury? I would think that any residual Hg in the tube would vaporize
with the heat of operation, presenting a real problem for the electron
emission getting to the plate. Any "gas" in a vacuum tube is usually
considered a bad thing.
I think that I had heard years ago that barium was most commonly
used.You did mention that it was oxidized, but I thought the oxide was
red in color. Most of my work with tubes was in lower power stuff, up
to, say, 6GL6, etc.
I remember there were some diodes (high current ?) that used mercury
in their operation, though.
The big ones are cool; I keep trying to get the engineer at our local
University station to save a defunct transmitter tube for me (I do a
weekly volunteer stint there as a DJ).
Joe
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