[AMPS] parasitics

[Jon Ogden]

>If it passes those tests AND as long as the suppressors are OK, I can in
>NO WAY accept that a parasitic will occur during use. Arcs on standby are
>gas or barnacles in the tubes....note that those arcs rarely if ever are
>associated with capacitor or switch failure but can blow grid chokes and
>tubes.

I've read Rich's information on his webpage and I think I can repeat his 
theory:

He says that whenever you have a change in anode current in a tube that a 
small, damped VHF signal will result.  He says you can observe this with 
an O-scope or a spectrum analyzer.  If there is enough Q in the VHF tank 
circuit in the PA, then an osicallatory condition could occur.

While I agree that the whole tank circuit in a tube IS VHF resonant, I am 
not sure of how a transient current condition in the tube can produce a 
VHF ringing.  I would like to know if anyone has seen this on a piece of 
test equipment.  If true, it does add a lot of credence to Rich's 
theories.

ALL tubes contain parasitics.  There is a BIG difference between a 
parasitic and a parasitic oscillation.  It's easy to get them confused.  
A parasite in a tube is the lead inductance and stray capacitances, etc. 
that exist in the real world.  Even a leaded capacitor has parasitics 
(lead inductance).

73,

Jon
KE9NA


--------------------------------------------------------------------------
Jon Ogden

jono@webspun.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."




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