[Amps] Re: Voodoo "EMF' forces from grid current pulses

[2]

>2 wrote:
>>The grid wires in all of the shorted 3-500Z and 3-400Z tubes that I 
>>have autopsied appear to be straight.  I have never seen a bent grid. 
>>The bent element is the thoriated-tungsten filament helix.
>>
>>>you will have to come up with another mechanism, one that can generate some
>>REAL
>>>force.
>>>
>>There is no doubt that real force did the bending because real force is 
>>required to bend a bent filament straight.  It typically takes 11-G for
>>c. 40-seconds, with the filament operating at c. 5.6V, to straighten 
>>the
>>filament.
>
>Fine - so where *did* the force come from that bent it? Eric has just 
>shown that the EM force between two parallel wires is about 1/1000 of an 
>ounce for the conditions he assumed (two 1in wires separated by 1mm, 
>each carrying 10A). Even if you dispute the value of the current, you're 
>still adrift by several orders of magnitude.
>
If  electric current can move heavy Cu welding cables a few inches, the 
effect does not seem trivial.  

>>-  Eric --  How do you explain:
>>1.  the grid-filament short often seen in 3-500Zs often follows a 
>>big-bang?
>
>And just before the event, the grid and filament were already how close? 

New Eimac 3-500Zs have a grid withstanding potential of 8 - 9 kV.   The 
amount of bulge from the bent filament in a grid/fil shorted 3-500 is 
quite noticeable. 

>Nobody knows, because only totally dead tubes are ever autopsied.

The tubes I autopsy typically have grid-filament withstanding potentials 
of under 500v.   What could make the withstanding potential drop over 7kV 
during the first half-hour of use ? 
>
>>2.   the simultaneous burnout of a grid choke made from 28ga Cu wire?
>>
>That shows that considerable grid current had flowed - but nothing more. 
>You still don't know whether the blown choke and the grid-filament short 
>were both caused by the "main event" at the same time; or whether that 
>event only caused the grid-filament short, which then blew the choke as 
>a follow-on.

The fusing current of #28 Cu is considerably higher than a TL-922's or a 
SB-220's 110vdc supply can furnish.  Also consider that grid-filament 
shorts also occur in amplifiers that employ R-cutoff Receive biasing.
>
>Also there is conflicting evidence. On the one hand, enough grid current 
>has flowed (somehow) to burn out the choke. On the other hand, it's not 
>the grid that has bent - it's the filament.

Where does DC grid-current come from, Ian ?
>
>
>I'm sorry, but the evidence about this whole topic certainly does *not* 
>"speak for itself"... at least, I can't hear the voices :-)
>
**  Autopsy a shorted 3-500Z and you may receive a clue.

>We're back again to the limitations of autopsy evidence, and the need to 
>sometimes return an Open Verdict.
>
**  only if the jurors assume that feedback-C is not important.  

-  R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K, 
www.vcnet.com/measures.  
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