[AMPS] Self oscillation with homebrew 3-1000Z ????

[Tom Rauch]

Is this ten meters ONLY?

> and it seems ok at 1500volts. Put 3KV on it and it will make a few
> watts of power without even putting RF to it. I heard a small RF type
> arc- kind of like slight arcing in an air variable, (I have a vaccum
> cap) the tube glowed red and I quickly unkeyed it. I turned the load
> and tune caps a bit, tried it again- it was quiet for about 2 or 3
> seconds- then it did it again.

Could be many things. How long are the leads from the anode to 
the tuning cap? Is the tuning cap mounted to the same sheetmetal 
as the tube grid is grounded to? Is the loading cap on that same 
sheet metal, or do both the tubes have a very solid very wide and 
very short return path back to the grid area from the tuning and 
loading caps?

What is the suppressor? How did you make it?

What about relays? What type? How much feedthrough around 
relays?? 

How are the grid pins grounded? How long are the leads?

There are a hundred things that you could do wrong, but the amp 
should be unconditionally stable even if the input and output are not 
terminated when you test it...if you do things right.


73, Tom W8JI
W8JI@contesting.com 

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