Western Electric is going to make tubes?

[Rob Strand]

But why are vacuum cleaners so loud?  (h.t. Duck's Breath Mystery Theater)

They move the noisy air from the inside to the outside.

This thread reminds me of the time, not so long ago really, that I could pop down the road to the Chelmer Valve Company trade counter and collect whatever I needed. EL34's for about £5, 12AX7 £3.50 etc.etc. So local and so cheap that I never felt the need to keep my own stock. Doh!

We had TV parts places here that kept a zillion tubes.  Even obscure ones.  The tubes were so cheap I got a few spares so I didn't have to travel.   The shops vaporized quite quickly.

Even Dick Smith electronics stores sold a decent number of tubes.  However, you can see early as 1977/1978 they kept quite a few but note manufacturers have stopped making some tubes.



By 1981/1982 the list has shortened somewhat, with a note about some unlisted tubes still might be in the store.  The 6CA7's have been dumped.



(FWIW, no tubes stocked in 1983/84)

[duck_arse]

...... no, nevermind.

[PRR]

This rendition of "Western Electric" goes back long before the current fad for "Hi Tech in the US" (but not as far back as the collapse of the Bell System).

The metal tubes did not hold vacuum any better than the glass ones. They were expected to be more rugged; also not throw light up on the wall behind the radio at night. But they cost a few pennies more and nobody wanted that. The US types introduced as metal soon sported glass equivalents. No new metal types were produced after WWII, though metal 6L6 were still made almost to the 6L6GC era.

It takes approximately forever to "suck" all the air out. You can't actually suck the last molecules, you have to wait until they randomly wander into the exhaust port and then carefully prevent them from wandering back into the tube. A few types were pumped for a week. Most types got a short hour. In either case it is usually necessary to "getter" the residual gas and any 'new' gas that was trapped in the metal and mica.

[Rob Strand]

The metal tubes did not hold vacuum any better than the glass ones. They were expected to be more rugged; also not throw light up on the wall behind the radio at night. But they cost a few pennies more and nobody wanted that. The US types introduced as metal soon sported glass equivalents. No new metal types were produced after WWII, though metal 6L6 were still made almost to the 6L6GC era.

An interesting thing about glass vs steel is how the heat is removed from the tube.   In a tube the *internal* heat can only be removed by radiation (and some conduction through the base) because there is no air.

In the case of steel the radiated heat is obviously blocked by the steel, the steel must absorbed the radiation in the inside then conduct it through the sheet and radiate and convect it from the outside.   In the case of glass it's not so clear  .  Glass seems to let light through but it actually blocks infrared.  So there's probably little difference between glass and steel.

See figure 1,
https://www.robertribando.com/wp-content/uploads/2021/02/Transmissivityglass.pdf

[Fancy Lime]

Okay, but it's gonna wind up like electric cars and lithium batteries vs. oil reserves, which country has the most abundant supply of the vacuum gas that goes inside the tubes?  And what happens to the vacuum gas that gets spilled while they twist the ends of the tubes?  And...

It was my understanding that vacuum gas is extracted from public officials.  So whichever nation or region has more of those will become the kingpin of tubes.

Just out of curiosity, at one time, many tubes had a metal casing, rather than glass.  Did that permit creation of a true vacuum internally?

Nah, these days it can just as easily be extracted from "social media". Instant global access to the deepest darkest void.

[PRR]

In the case of glass it's not so clear  . 

As you say: cheap glass is IR opaque. Radiation from guts to glass (also a pinch of conduction down the leads), then a mix of convection and radiation (and pinch of conduction for miniature types) to ambient. At receiving tube temperatures convention typically dominates over radiation, slightly.

[imJonWain]

I think it's much easier for a company to make choices based on personal beliefs or goals when they are privately owned and don't have shareholders or other investors to answer to.

[PRR]

......they experimented with partially evacuated tubes leaving some gas in there, but it was determined that a fully evacuated envelope was the way to go....

Gas tubes never went away. They conduct far better than empty vacuum. All fluorescents. All neons, little pilot and giant Las Vegas (tho now a niche industry). I'm sure some trashcan-size thyratrons are still used in electric railroads. Also airport radar. Maybe in >100KV DC power links. And all the switching in classic old-tech jukeboxes, which are as often lovingly restored as rip-n-bodged.

You are right that the idea of a trace of gas in the '01 to goose its gain dead-ended quick from excess noise.