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

[Kenneth G. Gordon]

Haw, haw! Yes, Les, you are SOOOO right. :-)

Ken W7EKB


On 14 Nov 2013 at 17:16, Leslie Smith 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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Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne