i wonder if induction heating on a dead heater would work

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i wonder if induction heating on a dead heater would work

Postby Harry Dalek » Tue Jan 24, 2017 4:28 pm

A while back looking at induction heating circuits and flame triodes diodes an idea has come to mind .
I have seen it used to heat a valve to burn off any impurities as its removing air for the vacuum.
If it was used on a valve with either a dead heater or heater not in use would the valve act as it does in a flame triode experiment ? and work in this case heating every thing as well as the heater ...may be you can localize it lower area of the tube heater area .
I can only think the frequency on the induction coil would might cause induced interference ...the 60 hz ac on a heater doesn't cause a problem...some thing to wonder about :lol:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: i wonder if induction heating on a dead heater would wor

Postby Klaas Robers » Wed Jan 25, 2017 9:27 pm

Harry, the trick of electronic valves is that the cathode is hot and the anode is cold. The hot cathode emits electrons, because the fast moving atoms at the surface loose electrons into the vacuum. The anode (plate) can attract the electrons, but cannot emit them as well, as the anode is cold.

If everything is hot, every electrode may emit electrons and you end up in a mess. That is the general story.

On the other end, the cathode is made of, or covered by a layer of material, that emits electrons easily, as easily as possible. Then the cathode can be as luke warm as possible. In the beginning cathodes were made of tungsten wire, which needed to be white hot to emitt enough electrons. Then lots of research was done, a.o. in our Philips Research Lab in Eindhoven, to find materials to coat the tungsten wire with, that emitted electrons much better. So the cathode needed to be not hotter than dark orange or bright red. This was really a very important research, where several men contributed in.

The problem for your idea is that induction heating makes the outer electrodes (anode) the hottest, and the inner electrodes (cathode) are shielded more or less for the heating power. So heating from the outher side is the worst thing you can do. You should heat the valve from the center and that is done by the filament inside the thin cathode tube. If that is interrupted, the tube is gone and you have to find a new one, or at least a better one.

The induction heating of electron tubes that you have seen is to evaporate remains of air and other gasses from the electrodes, and to form the "silver" mirror inside the glass bulb. This mirror is made of material that catch in gass atoms, in order to keep the bulb vacuum. It is called "getter". This "pumping" after the tube is closed works best at somewhat higher temperatures. That is the reason that old valves have to be run first for several hours with only the heater on. Then when most of the gasses are removed, you may switch on the anode voltages.
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Re: i wonder if induction heating on a dead heater would wor

Postby Harry Dalek » Thu Jan 26, 2017 8:37 pm

Klaas Robers wrote:Harry, the trick of electronic valves is that the cathode is hot and the anode is cold. The hot cathode emits electrons, because the fast moving atoms at the surface loose electrons into the vacuum. The anode (plate) can attract the electrons, but cannot emit them as well, as the anode is cold.


Ok Klaas thats something i didn't think of so i suppose when the Triode or what ever heats up it must become less efficient and become more noisy makes sense.

If everything is hot, every electrode may emit electrons and you end up in a mess. That is the general story.


On satellite lnbs you reduce the electonics noise if you can cool the things as cold as possible and receive the universe noise with out the electronics adding to it ....or least as possible .
Wonder it they ever cooled valves ?

On the other end, the cathode is made of, or covered by a layer of material, that emits electrons easily, as easily as possible. Then the cathode can be as luke warm as possible. In the beginning cathodes were made of tungsten wire, which needed to be white hot to emitt enough electrons. Then lots of research was done, a.o. in our Philips Research Lab in Eindhoven, to find materials to coat the tungsten wire with, that emitted electrons much better. So the cathode needed to be not hotter than dark orange or bright red. This was really a very important research, where several men contributed in.


I was thinking of a few ideas on the induction idea to have the flat coil at around the base of the tube below the Anode some valves theres a amount of space between the base and wiring to the bits in the tube ..if you can heat the wiring to the heater by an adjustable amount via induction there might be a sweet spot but i know here it would also heat the control and anode wires to them also here ..another idea again on induction if you had a small tiny induction coil spaced around one of the heater pins only inducing heat to that heater pin wiring that might work need a small ceramic spacer for the coil not to short out .
my idea would be much smaller than this one for a tube pin .
https://www.youtube.com/watch?v=sodeAmFli7I

The problem for your idea is that induction heating makes the outer electrodes (anode) the hottest, and the inner electrodes (cathode) are shielded more or less for the heating power. So heating from the outher side is the worst thing you can do. You should heat the valve from the center and that is done by the filament inside the thin cathode tube. If that is interrupted, the tube is gone and you have to find a new one, or at least a better one.


I wasn't sure a less fussy coil might do the trick but your advice on it having to keep the heat away from the anode and i also see on nylesteiner's Flame triode the flame is kept away from the Anode also.
https://www.youtube.com/watch?v=-aAwyUo ... UQ-YTPZNfu

The induction heating of electron tubes that you have seen is to evaporate remains of air and other gasses from the electrodes, and to form the "silver" mirror inside the glass bulb. This mirror is made of material that catch in gass atoms, in order to keep the bulb vacuum. It is called "getter". This "pumping" after the tube is closed works best at somewhat higher temperatures. That is the reason that old valves have to be run first for several hours with only the heater on. Then when most of the gasses are removed, you may switch on the anode voltages.

[/quote]
Yes i found this very interesting when i saw a video of it once very clever procedure to come up with .
Knowing what should be done and what not to do i still think Klass with your advice it might be possible adjusting the voltage to the induction coil a bit fidelity the trick now with understanding would be Localising this effect a few pictures mock up for a future try some time ....i made a ZVS high voltage inverter a while back works well /..have not tried the induction version yet .
Another trick might be winding a copper wire around the heater pin tight with the long bit of wire from it sticking out and heat it with a candle bit harder adusting the temperature might be fun for an experiment .
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Harry Dalek
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