[Milsurplus] [Boatanchors] Smart People: Gassy Tubes Reversable?

[hwhall at compuserve.com]

 Does that perhaps imply that some of our gas troubles may be from the typically intermittent nature of amateur operation? I recall claims made to me long ago that leaving amateur gear on fulltime instead of shutting off after each operating session/day made tubes last longer, but their thinking related to preventing filament burnout. Perhaps there may be a gas capturing benefit as well?

Is this what happens: though hot tube elements outgas faster, the getter material is also mopping up quickly with heat enhanced chemical reactions, and a point may be reached where outgassing slows and the getter cleans it up.

Thanks!

Wayne

 

-----Original Message-----
From: J. Forster <jfor at quikus.com>
To: hwhall <hwhall at compuserve.com>
Cc: arc5 <arc5 at ix.netcom.com>; boatanchors <boatanchors at mailman.qth.net>; milsurplus <milsurplus at mailman.qth.net>
Sent: Tue, Dec 3, 2013 2:14 pm
Subject: Re: [Boatanchors] Smart People:  Gassy Tubes Reversable?

 
 
 
As I've written before, if you run the tube with filament and plate 
voltage, biased to 10%-20% of nominal Ip for a couple of days, many tubes 
clean up and become gas-free. 
 
-John 
 
==================== 
 
 
 
> Yes, that all rings with what I remember from physics classes. So tube's 
> can get gas from outside the envelope as well as from internal outgassing. 
> Which unfortunately still leaves us with the questions of whether there 
> are practical cures. The links provided by VE3BBM and W5JO seem to provide 
> some material for thought & experiment. 
> 
>  Wayne 
> WB4OGM 
> 
> 
> 
> -----Original Message----- 
> From: J. Forster <jfor at quikus.com> 
> To: hwhall <hwhall at compuserve.com> 
> Cc: arc5 <arc5 at ix.netcom.com>; boatanchors 
> <boatanchors at mailman.qth.net>; milsurplus 
> <milsurplus at mailman.qth.net> 
> Sent: Tue, Dec 3, 2013 1:19 pm 
> Subject: Re: [Boatanchors] Smart People:  Gassy Tubes Reversable? 
> 
> 
> 
> 
> Yes, 
> 
> Gasses diffuse through glass, even if the metal-glass seals are perfect. 
> 
> It depends on: 
> 
> Pressure differential 
> Glass permeability 
> Gas molecule size. 
> 
> If you have a glass Dewar and you leave it exposed to He overnight, it'll 
> be useless the next day. The He will diffuse through the glass and spoil 
> the vacuum. HeNe LASERS die for the same reason. 
> 
> BTW, gasses diffuse through metals too. Hydrogen diffuses through hot 
> Palladium very well. That's how untra-pure H2 is made. 
> 
> This same physics is use to enrich uranium, as in Iran. 
> 
> -John 
> 
> =================== 
> 
> 
> 
> 
> > > 
> > The diffusion rate through a semi-permeable membrane detends on the 
> > pressure difference across the membrane. 
> > > 
> > 
> > Hi, John. I think you are referring to gas diffusing through the tube 
> > envelope? I hadn't considered that. I was assuming gas "leaking" in 
> or out 
> > via wire lead seals, sort of like through nano-cracks between 
> materials. 
> > 
> > 73, 
> > Wayne 
> > WB4OGM 
> > 
> > 
> 
> 
> 
> 
> 
> 
>