[AMPS] Follow Up on the SB-220 Follow UP

[Jon Ogden]

>> If you 
>>think that he had a parasitic event while unkeyed, please explain how 
>>this could happen.  I always belived that a tube in cutoff would be very 
>>hard to get oscillating.  You also told me this once.
>>
>€  The how part beats me.  It has not happened to me, however, I have 
>talked to a number of those who have had it happen.  How do we know it 
>was a parasite?  Bent fil. helix / sudden change in suppressor resistance 
>/ 6kV bandswitch arcs in amp. with 3kV anode supply, are clues.

I guess it happens to those who think that every bang is a parasitic oscillation.  For one, with proper suppressor resistors you shouldn't have an oscillation.  I don't think the oscillation changes the value of the resistors.  Rather, I think the resistor values change over time and over being heated up.  Then you can get an oscillation because of bad resistors and hence a suppressor not performing properly.

But the only thing that blew in this guy's amp was a resistor.  Don't think he had the beloved parasite.

73,

Jon
KE9NA


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

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

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


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