[ARC5] Smart People - OT Why pentods fail (was Triodes & Pentodes)

[Bruce Long]

leslie is WRONG

Electrons have no weight at all.   But they do come in pairs as male electrons and female electrons. Otherwise where would little electrons come from?  As they accumulate on the screen they have no place to go and they get crowded closer and closer together.   Eventually nature takes its course and they get hot?

Understand?





On Thursday, November 14, 2013 1:00 PM, Tim <timsamm at gmail.com> wrote:
 
Hi Les - Thanks for explaining that....Very interesting!  I had previously
thought that the main failure mode was caused by the vacuum leaking out.
Who knew?
Tim
N6CC


On Wed, Nov 13, 2013 at 10:16 PM, Leslie Smith <vk2bcu at operamail.com> wrote:

>  "The screen failure will not be due to voltage over max but excess
>  dissipation."
> >
> > I agree.
> >
> > Ken W7EKB
>
> Aw- Ken!
> The above is nonsense, and I'm onto you.   :-;    It's not dissipation
> (I-squared R heat) that causes the damage.
>
> The screen sags from the weight of accumulating electrons; the flow of
> electrons is impeded by the thin wire.  :-(
> We get the word, impedance from the latin, "impedire", meaning "to
> shackle the feet" - and this is exactly what the thin grid wire does -
> it impedes those little electronic feet.
>
> Note:  Screen-grids built from thicker wire allow the electrons to
> escape; there is no sagging.  :-)
> As for the the plate - it doesn't sag even a little.  Being thicker and
> more robust, it can take the weight.
>
> As more electrons accumulate the screen grids sags, more and more, until
> it touches the cathode.
> The resulting short circuit  results in a decent "bang!".
> This is the true failure mode.  Trust me.
> I know nearly list-reader here will agree, particularly the better
> informed readers.  :-) :-)  :-)
>
> Les
>
> (PS  I hope I don't get banned from  the list for stating the truth)
>
> --
> http://www.fastmail.fm - A fast, anti-spam email service.
>
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