Amps
[Top] [All Lists]

[AMPS] Linear AMP timing

To: <amps@contesting.com>
Subject: [AMPS] Linear AMP timing
From: 2@vc.net (2)
Date: Thu, 9 Aug 2001 10:42:28 -0700
>
>> >>In all this discussion, nobody has mentioned the bias switching.  IMO,
>> >>the amp should not be biased on until all the relays have closed and
>> >>must be biased off before any of them open.  
>> >>
>> >
>> >/\   Please explain why.
>> >tnx
>> 
>> _________________________________________________________
>> 
>> It will make it impossible for a tube to be momentarily unloaded, either
>> at the input or output.  
>
>Bill, What actually 

//  (key word)

>...will happen ios the tube becomes a dc cathode 
>follower, and the cathode voltage easily pumps up a bit higher than 
>you might expect.
>
//   The 3-500Z filaments/cathodes connect directly to the +110vdc PS 
whenever the T/R relay bias contacts open.  In a g-g 3-500Z, running at 
3kV, cathode current is essentially cut off with c. +23v on the cathode 
because the grid looks 23v negative with respect to the cathode .  At 
+110v, the tube is undoubtedly cutoff..  How can zero cathode current 
"pump up" anything?  It seems to me that someone is pumping blarney.  


>Then the relay has to discharge any capacitors, 

///  The relay NC contact is required to instantly charge the 2x 0.02uF 
of filament winding bypass-C to 110v  whenever the T/R relay switches to 
receive.  

>plus handle some 
>instant peak anode current while bouncing.
>
>That might wear on the relay, but I'm not sure at all it is any worse 
>than a small RF spark on the input relay. 
>
>My gut feeling is it is better long-term to not close the input relay 
>early or open it late...compared to the output relay. But that is only 
>a gut feeling.  

//  ... that is seemingly not based on logic.  

>73, Tom W8JI
>W8JI@contesting.com 
>
cheers

-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  
end


--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com


<Prev in Thread] Current Thread [Next in Thread>