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

[measures]

>
>A problem for all the experts-
>I Built a 3-1000Z monoband amp for 10 meters.  I Sowly Variaced it up 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. I have a 
>similar homebrew grounded grid 4-1000A amp and never had a problem- it 
>worked 
>great the first time I fired it up! I built the 10 meter mono-bander because 
>I cant get the 4-1000A amp to work on to good on ten- but it works great on 
>the other bands. Any suggestions??   

3-1000Zs have much feedback capacitance - which is why they oscillaate.  
I would try decreasing the RL of the parasitic oscillation suppressor.  

>Keep in mind- I have yet to even hook a 
>rig to this- just a dummy load- I variaced it up, saw idling current, and it 
>started to run away.


good luck, Jim
>


-  Rich..., 805.386.3734, 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