[AMPS] Rocky Point effects

[measures]

>
>Rich Measures wrote:
>>
>>>
>>>It has always appeared to me that normal well documented arcs 
>>>and sparks in tubes have been used to sell nichrome.
>>>
>>Tom -- My position has always been that unless gas is subsequently found 
>>with a high-pot., an arc is not logical.  Tom's answer is that the gas 
>>disappeared because of gettering.  Is gettering very likely while the 
>>tube is being removed from the amplifier for high-pot. testing?
>>
>Yes. If there is a small gas release, the gettering action (which
>depends on the gas molecules colliding with the metal surfaces) would
>take place on a timescale of seconds. 

A big bang is heard.  The main breakers blow.  What souce powers the tube 
during the gettering?  It is my opinion that instant gettering is 
undiluted codswallop.  

> That's way too slow to prevent an
>arc, but fast enough to clean up the vacuum before you can get the tube
>to a hi-pot tester. 
>
>>
>>>Terry's amplifier very well could have been the victim of just such a 
>>>common effect, but since it is not nearly as well publicized outside 
>>>engineering circles as parasites it is overlooked.
>>>
>>Barnacles that disappear?
>>'
>Microscopic 'whiskers' may be a better term. They can start an arc by
>field emission, but are burnt off by the high current density.

With copper atoms, yes.  I have never heard of tantalum atoms forming 
whiskers.  When copper whiskers arc and burn away, a slight tink sound is 
heard.  
>
>
>However, I'm still uneasy about Terry's experience, because that seemed
>to be reproducible on demand, which is not characteristic of a random
>event like an arc. 

The 2K-4 has some fairly unique resonances.  The anode-resonance is 
c.95MHz.  The 29uH HV RFC has a resonance near 95Mhz.  The output 
compartment appears to have a resonance near the same frequency.  My 
guess is that the resonance freq. of the output compartment can be 
slightly tuned by lifting the lid.  .  When a 2K-4 has a parasite, 
several turns of the HV RFC are typically  toasted
>
cheers, Ian


-  Rich..., 805.386.3734, www.vcnet.com/measures.  
end


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