Heated Outer Grid

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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guest

Heated Outer Grid

Post by guest » Thu Nov 15, 2001 4:14 am

Has anyone tried this......Use heating element wire(ie.similar to what is used in a space heater)to form the outer anode grid. Power it up(red hot), then apply the high voltage to it; similar to an x-ray tube. This should provide considerably more output. As far as modifications are concerned, this wouldnt be too difficult.

Just a thought I had on the way home from work today.

Mark R.

guest

Re: Heated Outer Grid

Post by guest » Sat Nov 17, 2001 7:51 am

It should be feasible to make one in a similar way to the large thoriated tungsten wire basket filaments that ceramic transmitter tubes use, possibly from tungsten welding electrode wire, but it would need to be activated with carbon to get any decent electron emission.

guest

You lost me on that.......

Post by guest » Mon Nov 19, 2001 8:01 pm

Does this mean that the anode in a heated electron tube (ie. 3B24W or 6L6 ) is carbonized ? I thought the basics of thermionic emission would dictate a substantial increase even without a carbon activator. Now I am a bit confused on this. Could you elaborate ? Thanks

guest

Re: You lost me on that.......: have a look at this

Post by guest » Tue Nov 20, 2001 7:59 am

Hi Mark, there's a pretty good explanation on carburizing filaments of ceramic style power tubes at http://www.eimac.com/sec2-4.htm which explains the filament treatments used in the tube industry, according to that it's just a way of increasing tube life rather than activating it as I said earlier. This website gives some info that may be useful with regard to activating a tungsten filament to get good emission, more or less giving it a few well judged over voltage boost to get some thorium on the surface

guest

Re: have a look at this

Post by guest » Tue Nov 20, 2001 8:00 am

I forgot to add this URL about activating an old filament: http://www.antiqueradios.com/chrs/journ ... ation.html

DaveC
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Re: have a look at this

Post by DaveC » Tue Nov 20, 2001 8:23 am

I think the method of applying an overvoltage to the filament for a short period of time is(was) used to rejuvenate CRT's too. Some protable CRT testers had the circuitry built in.

Dave Cooper

guest

Thanx !....That makes sense(N.M.)

Post by guest » Tue Nov 20, 2001 11:53 pm

NM

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