[Milsurplus] Smart People: Gassy tubes , again

[J. Forster]

BAMA would be a better bet, The manual is much more likely to have a
theory of operation.

-John

===============



>  The surplus store has several of those in a bin. Next trip there, I'll
> see if any have instructions printed on them.
>
> Wayne
>
>
> -----Original Message-----
> From: J. Forster <jfor at quikus.com>
> To: hwhall <hwhall at compuserve.com>
> Cc: ramcam <ramcam at magma.ca>; milsurplus
> <milsurplus at mailman.qth.net>
> Sent: Tue, Dec 3, 2013 4:28 pm
> Subject: Re: [Milsurplus] Smart People: Gassy tubes , again
>
>
>
>
> I don't know much about CRT rejuvenators. It was discussecat length on the
> HP_Agilent list a while back. Their operation must be discussed in the
> literature, or maybe in the instruction manuals from maybe Sencor or B&K.
>
> -John
>
> =====================
>
>
>
> > I thought Ralph's reference to the 10 percent boost applied to tubes
> in
> > general. I did know that strongly heating a filament was reputed to
> drive
> > off accumulated contamination in some cases. But what that had to do
> with
> > helping the getter, I didn't 'get'. Or was the point perhaps that by
> > releasing it from the cathode the getter was able to 'get' at it &
> was
> > helped in that way. (Sorry for the puns, couldn't help myself.)
> >
> > One reads a lot of reports about how to rejuvenate tube cathodes, but
> the
> > ones that seem most credible are the ones that take the different
> cathode
> > chemistries into account. Though cathodes get poisoned by gas,
> perhaps I
> > ought not stray so far from the original issue of gas removal into a
> new
> > (yet old) cathode rejuvenation topic.
> >
> >
> >  Wayne
> >
> >
> >
> > -----Original Message-----
> > From: J. Forster <jfor at quikus.com>
> > To: hwhall <hwhall at compuserve.com>
> > Cc: ramcam <ramcam at magma.ca>; milsurplus
> > <milsurplus at mailman.qth.net>
> > Sent: Tue, Dec 3, 2013 3:12 pm
> > Subject: Re: [Milsurplus] Smart People: Gassy tubes , again
> >
> > >     I remember those, but as I remember them, the rejuvenators
> were
> > > installed and left in place for the remaining life of the
> picture
> > > tube. It's easy to see how the higher temperature can
> comepensate for
> > > a cathode's waning emission ability.
> >
> > Yes.
> >
> > > I don't understand how running the filament at boosted voltage
> for
> > only
> > > 20 mins affects the getter function. Is it because the getter
> flash
> > > material gets hotter? If so, would longer times also make a
> greater
> > > difference for tubes with more gas?
> >
> > No. A picture tube has a large surface area. The amount of gas that
> > diffuses in is proportional to surface area, all other things being
> equal.
> >
> > Now, when a gas atom is struck by an electron, it acquires a
> (+)positive
> > charge, so it flees the plate and moves toward the cathode. When it
> > impacts the cathode, it 'poison's' the cathode. An increased voltage
> for a
> > short time, 'boils' off this poisoning to some extent, cleaning the
> > cathode and improving emission.
> >
> > This is why I suggested running a tube at 10% to 20% of rated
> current. If
> > you degas at higher Ip, the cathode gets poisoned and Gm goes down.
> >
> > BTW, I -think- that the TV rejuvenators are used with the electron
> gun
> > biased off, but am not cert6ain.
> >
> > FWIW,
> >
> > -JOhn
> >
> > =================.
> >
> >
> >
> > >
> > >    Wayne
> > > WB4OGM
> > >
> > >
> > >
> > >  -----Original Message-----
> > >  From: Ralph Cameron <ramcam at magma.ca>
> > >  To: milsurplus <milsurplus at mailman.qth.net>
> > >  Sent: Tue, Dec 3, 2013 9:18 am
> > >  Subject: [Milsurplus] Smart People: Gassy tubes , again
> > >
> > >
> > >
> > >
> > >  One may remember the trick of restoring CRTs that had lost
> emission
> > due
> > >  to filament contamination. Some of the so called "CRT"
> rejuvenators
> > >  boosted the filament voltage with directly heated cathodes to
> burn
> > off
> > >  some of the accumulated "junk" in the vacuum. Most of this junk
> was
> > >  metal contaminants. A 10% boost in filament voltage for 15-20
> mins
> > may
> > >  help the getter.
> > >
> > >  Ralph
> > >  VE3BBM
> >
> >
> >
> >
> >
> >
> >
>
>
>
>
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