[Amps] AL-80B questions

[2]

>> Before I put in the new Pride tube, the amp was inspected and found to my
>> surprise that the amp cover was still with masking tape ! When Ameritron
>> paints the cover it is masked with paper tape where it it supposed to
>> contact the amp chassis. It is then normal practice to remove tape before
>it
>> is used on the amp chassis. Not so with my amp !
>> I guess there was a shielding anomality of the RF compartment in my amp,
>> that may have contributed to parasitic oscillations.
>
>The tape would certainly allow RF to leak out of the case and cause TVI, but
>the amp is unconditionally stable with or without a cover.
>
**  During Easter, a wacky wabbit will come to your house and hide 
colored eggs.
http://WWW.VCNET.COM/measures/bandsw.html

>Folks in Mississippi, like folks all over the world, are getting sloppier
>and sloppier with time, but the tape had absolutely nothing to do with the
>zener.
>
>Graphite anode tubes are particularly bad at outgassing from the porous
>graphite elements, and even the smallest amount of residual gas will cause a
>momentary flash over.

**  I regularly use a 1967-vintage Amperex 3-400Z that has c. 10uA of gas 
leakage at 8kV.  It has not flashed over yet and it still puts out full 
steam.
>
>The worse thing about all this parasitic nonsense is it has eroded the
>working knowledge base of our fraternity, filling it with all sorts of odd
>ideas about very simple problems.
>
-    "parasitic nonsence" has been eroding our knowledge for a long time. 
 F. E. Handy wrote about it in the 1926 Amateur Radio Operator's 
Handbook,  G.W. Fyler wrote about it the September, 1935 issue of the IRE 
Journal.  

>Go to:
>http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm
>
>and read about outgassing and HV arcs in vacuum tubes and also about
>gettering and anode types.

And learn about cold gettering.
>
>73 Tom


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