Pickle Jars and Vacuum Tubes

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Pickle Jars and Vacuum Tubes

Post by Ragwire on Fri Jun 12, 2015 10:54 pm

Why not make a tube? Well there are lots of reasons to not make tube, but I am unreasonable.   Neutral

...Slowly making progress. I may need to go to a coaxial layout in order to get gain. This one passes a signal--inverted on the plate load, as it should be--but is only about 1/2 the amplitude of the grid signal.
I gave up on metal filaments. Tungsten is too hard to work with. I switched to carbon in the form of a graphite mechanical pencil lead. The work function of carbon is a little lower than uncoated tungsten, too, so I can run it a bit cooler and still get decent emission. It's a power hungry little beast though; it draws about 8 amps at 12 volts, hot.

The brass fitting partly seen at the top is the vacuum port.




This carbon filament has several hours use on it and still looks perfect:



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Re: Pickle Jars and Vacuum Tubes

Post by Wildcat445 on Sat Jun 13, 2015 12:58 am

I admire your hutzpah. You have more energy than I do. I think I've done well to pull a tube out of the box and test it, let along build one. Good luck.

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Re: Pickle Jars and Vacuum Tubes

Post by Ragwire on Sat Jun 13, 2015 9:50 am

Nah, I just don't watch much TV. I'd rather do something! Laughing
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Re: Pickle Jars and Vacuum Tubes

Post by 75X11 on Mon Jun 15, 2015 2:35 pm

Wonder how structural carbon fiber would do for a filament?
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Re: Pickle Jars and Vacuum Tubes

Post by Bill Cahill on Mon Jun 15, 2015 6:31 pm

It, lamploc, and, many other things were tried by Edison while working on the electric light. Most failed quickly. Carbonized thread worked best.

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Re: Pickle Jars and Vacuum Tubes

Post by Bill Cahill on Mon Jun 15, 2015 6:32 pm

Eventually, Tungston was found best.

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Re: Pickle Jars and Vacuum Tubes

Post by 75X11 on Mon Jun 15, 2015 8:09 pm

That is what I was thinking. The process for making carbon fiber resembles what Edison used in making the carbonized filament. It should work well in a diode as Edison stumbled upon it when trying to keep the carbon deposition from covering the bulbs' interior. He modestly called it the Edison effect.
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Re: Pickle Jars and Vacuum Tubes

Post by Ragwire on Tue Jun 16, 2015 1:52 pm

Graphite pencil lead works far better than anything I've tried so far. I have had hours on my pencil lead before I broke it making adjustment inside the tube.

Getting a deep and uncontaminated vacuum seems to be the hardest part right now, unless I invest in an oil diffusion pump. They can be had used from labs for a couple hundred bucks on eBay, and there is little to go wrong with them, but I don't have the spare money or inclination to buy one right now.

I am going for a concentric layout this time. Trying to get gain when electrons are going around the grid instead of through it might be an issue.




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Re: Pickle Jars and Vacuum Tubes

Post by 75X11 on Tue Jun 16, 2015 4:27 pm

That work is quite impressive! What are you using for the envelope?
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Re: Pickle Jars and Vacuum Tubes

Post by Dr. Radio on Tue Jun 16, 2015 8:57 pm

Very nice!
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Re: Pickle Jars and Vacuum Tubes

Post by 75X11 on Tue Jun 16, 2015 10:33 pm

I'm sorry, but when I asked about the envelope, I should have asked if you had any ideas on a container that would retain the vacuum permanently yet. I know it can be hard to get and keep a high vacuum. I used to work in high altitude simulation of high voltage power supplies and made up some of the seals and ports. The results you are getting are truly impressive and I am sharing the descriptions with the folks here at work.
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Re: Pickle Jars and Vacuum Tubes

Post by Ragwire on Wed Jun 17, 2015 9:12 am

Thanks fellas!
I am using a new Kerr, "self sealing" canning jar. They will hold vacuum for as long as you want to store food in one, I figure. I am leaving the evacuation port in place and valving off the pump at the jar lid and capping it. That way I can remove the pump and get it out of the way, but re-evacuate the jar as needed.
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