Making a vacuum tube from scratch

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Viv
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Making a vacuum tube from scratch

Post by Viv » Sun Sep 21, 2008 7:57 pm

I just loved watching this guy practice his art, and yes its an art as he is working glass like we work metal, some thing of interest to me as i was originally trained on valves and high power supplies for them, later glass gave way to ceramics and the beauty seemed to go at the same time, some thing about a big pair of 805s glowing that gave song to the heart.

http://wanderlustmind.com/2008/09/21/va ... m-scratch/

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Mark
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Re: Making a vacuum tube from scratch

Post by Mark » Mon Sep 22, 2008 2:00 am

Quite a bit of talent there.
Presentation is Everything

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Re: Making a vacuum tube from scratch

Post by Viv » Mon Sep 22, 2008 11:40 am

Heres a link to his web site

French

http://paillard.claude.free.fr/

English (via google transclack)

http://translate.google.com/translate?u ... n&ie=UTF-8

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larry cottrill
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Re: Making a vacuum tube from scratch

Post by larry cottrill » Mon Sep 22, 2008 12:53 pm

Now THAT is really cool. Thought I'd just watch a minute or two, but of course I just HAD to stay for the whole show. I loved working with tubes back in my ham radio days (1960s). I used to go to sleep at night with a softly playing 5-tube superhet glowing on the floor nearby (the stamped steel cabinet was long gone).

The piano background song is the great Billie Holiday hit "The Man I Love". I knew you'd want to know ...

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Re: Making a vacuum tube from scratch

Post by Viv » Mon Sep 22, 2008 1:07 pm

Hi Larry

I note from his video information he is in his 70s and was an active experimenter in the 50s, I have a G1 call myself back in the UK and I will probably transfer my license to a Canadian call when we move and finally get Settled Quebec, I doubt many people know what a superhet is now.

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larry cottrill
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Re: Making a vacuum tube from scratch

Post by larry cottrill » Mon Sep 22, 2008 1:50 pm

Viv -

One of my Jr High science teachers gave me an old multi-band one that had once been in a monstrous and elegant solid wood cabinet. It was two chassis, one being the basic receiver and the other the power supply and final amp with a 12-inch speaker mounted right in the middle. Altogether there must have been 20 to 25 tubes in it, all ancient numbers from the 1920s and 30s. It all worked -- that thing sounded like a million dollars, with warm, rich tones radiating out of that massive speaker. Of course, it would be considered weak on the high end. Ha.

I have no idea whatever happened to that. It was left behind with my smallish Tesla coils and stuff, decades ago. I gave away my homebuilt transmitters and power supplies. They were very low-power CW (code) rigs. I probably still have my key buried in a box somewhere. I still have two nice code "buzzers" I could lay my hands on in a couple of minutes if I were at home. That's about all I have left from my ham days -- EXCEPT for a box full of nice parts that were going to go into a 1000 watt CW push-pull final amp!!! Ha ha! That includes a couple of ceramic tubes, probably much like you were just talking about, but these 1000 watters have external plates (with fine mesh cooling fins, of course). They mount in special air flow sockets, with little porcelain ring chimneys around them. What fun!

A few years ago, I got to go through a tour of the transmitter at AM station WHO (Des Moines studios, but the transmitter is in Mitchellville, about seven miles from where I live). They have a new transmitter (where you can't see anything), but they have the old one sitting there as a reserve unit for instant failover, and I got to inspect that extensively. The final amp is two tubes in a push-pull configuration, each one weighing over 100 pounds! A little mini block and tackle is arranged inside the cabinet so they can be changed out (the top of the external plate is a lifting eye!). Talk about heat -- those two tubes together drive 50,000 watts peak power! Man, THAT is the way to do radio. When you calculate a grid resistor for something like that, you'd better get it right. With cooling fins and all, the diameter of each tube was maybe 14 or 16 inches, the overall height about the same. Expensive, too, I'll bet. The antenna is a steel truss several hundred feet tall (whatever 1/4 wave would be at 1040 Khz), resting on a gigantic glazed porcelain pad. Unbelievable, really.

L Cottrill

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Re: Making a vacuum tube from scratch

Post by Viv » Mon Sep 22, 2008 2:10 pm

Hi Larry

Yes we all have a few parts for a big linear amp hanging around for years ;-) those ceramics sound like 4CX series probably 4CX250Bs as they were very common and cheap to run up to 1200 watts sb, the basis and chimneys were always an issue in england and commanded high prices, the big stuff I have worked on too, makes you feel warm all over when its running ;-)

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Re: Making a vacuum tube from scratch

Post by GRIM » Wed Sep 24, 2008 12:35 pm

Truly Amazing , there cant be too many people in the world with that kind of ability ,

Heres a photo of a tube we had running where i work , MACHLETT 5682 215 KW , this has since been rebuilt and now has a ceramic envolope , just not the same as glass,
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Al Belli
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Re: Making a vacuum tube from scratch

Post by Al Belli » Wed Sep 24, 2008 2:05 pm

Hi Larry,

A 1/4 wave antenna at 1040 Khz. is ( 234/1.040) feet = 225 feet high, assuming a velocity factor of 1.0

Al Belli
Last edited by Al Belli on Thu Sep 25, 2008 3:33 am, edited 1 time in total.

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Re: Making a vacuum tube from scratch

Post by Viv » Wed Sep 24, 2008 3:34 pm

Al Belli wrote:Hi Larry,

A 1/4 wave antenna at 1040 Khz. is ( 243/1.040) feet = 233.65 feet high, assuming a velocity factor of 1.0

Al Belli
Hi Al

they often bring it a bit lower by using a top loading via a capacitance hat, base loading with outdoor inductors can get scary at that power level ;-)

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Re: Making a vacuum tube from scratch

Post by larry cottrill » Thu Sep 25, 2008 2:57 am

Well, OK, a couple of hundred feet, then. That sounds right -- I used to fire a Zep antenna that was 33 ft of hard-drawn copper wire, and operated at 7 Mc (as we called MHz back then ;-). Later I got a nice vertical, so I'd have one that would "radiate equally poor in all directions". Ha.

There are no loading gimmicks on that tower. It is solid welded steel tubing from the pads that ride the porcelain right up to the red light on top. It is heavily guyed, with many porcelain insulators interrupting the guy wires. There is a BIG lightning arrestor gap to protect the transmission line, and I guess that's a wonder to behold in a nice thunderstorm. They also have a soldered brass scale model around 30 inches tall that was used to test the radiation pattern back in the late 1940s, at some VHF frequency, as part of the final engineering of the big one.

Once in a while they play a recorded phone call from a Des Moines guy who moved to PA and can get their signal at night. Back when I was at Fort Polk, LA in 1968, the cadre who were the night staff in the orderly room used to listen every night without fail -- WHO used to play the country hits at night in those days. Even modulated, 50 KW goes a long way once you get the Heaviside Layer correctly positioned. Ha.

L Cottrill

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