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[AMPS] 3-500Z amplifiers and grid current

To: <amps@contesting.com>
Subject: [AMPS] 3-500Z amplifiers and grid current
From: measures@vc.net (Rich Measures)
Date: Tue, 17 Mar 98 19:26:51 -0800
>
>On Tue, 17 Mar 98 11:14:14 -0800 Rich Measures <measures@vc.net> writes:
.........
>>I rarely see a tube with bent filament helixes that exhibits gas 
>>problems.  
>
>.........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, 
Carl.  
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 
>>chassis 
>>ground.  The path to the chassis can not be through the grid because 
>>the 
>>grid is already connected to the chassis.  .  How can such an 
>>occurrence 
>>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? 
rauchschnauzers? 
>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.  

cheers
Rich...

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


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