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[AMPS] 3-500Z amplifiers and grid current

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Subject: [AMPS] 3-500Z amplifiers and grid current
From: (Rich Measures)
Date: Tue, 17 Mar 98 20:09:44 -0800
>>- Perhaps it's not all that stretchy.    During Final Test, a well-used 
>>pair of tubes are typically plugged in whilst the frisky Eimac beauties 
>>remain safely tucked away in their factory-sealed boxes.  .  Should one 
>>expect that tired old tubes have as much gain as new tubes? .  .  .  I 
>>have a tube that was mfg. in 1967, which still works, upon which I will 
>>confidently wager a large pizza with 4 toppings and salad bar, that it 
>>won't oscillate.
>Fascinating discussion....
>What's the difference between the old tubes and new tubes?  Why would the 
>old ones not oscillate in an amplifier while the new ones would?  

As tubes age, gain decreases.  Less gain means less ability to oscillate. 

>......did Eimac change something in the design of the tubes?

Eimac decreased the Mu from approx. 190 to approx. 130.  The oscillation 
situation did not seem to change.  
>I gotta say, I am on your side in this one so far....but then again, what 
>do I know!  :-)
Carl has not yet proffered another explanation of how the filament gets 



postscript  I tried to send this to your e-mail address. Jon, and it was 


R. L. Measures, 805-386-3734, AG6K   

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