Tubes?

[innovation_station]

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what can i say


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merry christmas

i am genuine

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Histeam!!

[turbo]

i am genuine

Histeam!!

Hey , i'm genuine too..

I think we all are, aren't we?

M.

[Localjoe]

Man this song has a nice sound http://video.google.com/videoplay?docid=4119317559614871874

[Adeon]

HI All..

My first post here, and Im pretty interested in doing some testing to start with, and to do the testing I want to build a pulse circuit with frquency and pulse width modulation using a vacuum tube.. Id love your thoughts on this idea and the types of components to use.

The tube will be delivering pulses to the primary of our coil.

Switching voltages of around 100-500v

We need a Hard cut pulse with variable pulse width down to the microsecond and high frequencies 20khz +

We cant use silicon for this.  It must be a hard physical break and Vacuum tubes are the only thing I know of that can do those frequencies. I'm thinking a RF Valve Triode.

We can use silicon to drive the Tube Switch on and off.  I'm pretty sure a standard Radio Frequency tube would do it.  But the trick is the pulse width variable.

We need to be able to alter the pulse width down to micro seconds.  We need short sharp bursts.

OPTIONS :

Dual Switch operation.  So one control unit controls 2 switches, allowing us to switch both Pos & Neg line..

Custom Function generator to mathematically compute the pulse width and frequency using functions/formulas.  This would allow us to get exact frequencies and Pulse/Space ratios. Could use a Laptop and a little program to control that.  Or code a EPROM to do it. But we would need a good processor to run the high speed clock cycle for accurate microsecond pulses.

Multiples of this deisgn could be use for multiple freuqncies, and using a function generator to control the pulse width and frequency would allow you to create specific harmonics.

See attached diagram.
PS - Spark Gap is just for safely to protect any back EMF overload of the Triodes.

[Jdo300]

Hello All,

I'm back on the tube scene again and this time, I've abandoned the 6AU6 pentodes that I was using in favor of the 12J5 TV tube triodes that I found recently. These tubes are rated for RF frequencies (some were used as radio tubes) and also for the VHF circuits inside old TVs (See attached pic).

I am now working on a way to set these tubes up to act like high gain amplifiers. I essentially want to make the tube equivalent of a comparator. so that I can use SS  logic ICs like a 74HC04 NOT gate, which has a fast rise time, to 'trigger' the tube on and off. But I need some help finding the right circuit to configure the thing with. So far, I tracked down a simple triode amplifier schematic, but I'm not sure that it will give me what I want (also attached below). If there are any experienced tubers here on the forum who can help me, I would be most grateful 

God Bless,
Jason O