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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 19:26:51 -0800
>On Tue, 17 Mar 98 11:14:14 -0800 Rich Measures <> writes:
>>I rarely see a tube with bent filament helixes that exhibits gas 
>.........what does that have to do with the single brand new
>tube that you started this discussion with.  

Because the tube does not appear to have a gas problem and it 
filament/grid. shorted.  

>I sure hate drifty conversations. 
You have not explained the mechanism that caused the grid choke to blow, 
You have not explained the mechanism that caused the filament helixes to 
bend, Carl?  
>>>>By what mechanism does an allegedly defective tube damage the 
>>>>parasitic suppressor R and blow the grid choke?
>>>A big bang in an amp without a HV surge resistor.
>>A "big bang" undoubtedly involves some sort of positive hv arc to 
>>ground.  The path to the chassis can not be through the grid because 
>>grid is already connected to the chassis.  .  How can such an 
>>possibly damage the VHF suppressor R, which is paralleled by typically 
>>less than 0.001 ohm of copper wire?  
>I guess that your version of a failure path and mine differ a lot.  The
>DC and the  RF enhanced gas paths do differ.  

The explanations, please? 

>Something I learned as a kid....the path of least resistance....but at age 15 
I thought that
>meant                                                            SEX. 
seems sorta drifty
>>What is "real proof".  Tom Rauch suggested that I faked the 
>>photographs of the parasite-toasted bandswitches.  
>Who cares what Rauch thinks? 
>He may be right or wrong...his opinion is as meaningless as yours without
>proof.  "Reportedly" dont mean squat.
Is "squat"  a euphemism for "shit", Carl?  .  .  A friend ran the 
aforementioned test at his place of employment.  If I ran the test 
myself, you could claim that I faked the results.    

>>>Until that occurs I find it a real stretch to believe that a brand 
>>>new 9 year old amp and tubes would harbor a dreaded parasitic at turn-on. 
>>- 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? .  .  
>Maybe in your version of reality.  In the real world amps are final
>tested AND shipped with the same tubes. 

The 3-500Zs with the TL-922 were in unopened Eimac boxes.  
>> 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.  .  
>A tube....6L6 or what??  I have been thru scores of 3-500Z amps that seem
>to run forever with the original 196x-7x era tubes. It is the later Eimac
>years that fuel the fire....
Thousands of 3-500Zs reportedly filament/grid shorted in early production 
SB220s.  As I recall, the SB-220 was introduced c. 1969.  


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

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