[SignalOne] Arcing in Final

[W2AGN]

OK, this is driving me nuts! About 4 months ago I became the proud owner 
of a lovingly restored CX7A. It looks like new. First time I turned it 
on...ka-pow, the 1 ohm resistor blew. Talking to the gentleman I bought 
it from, it seems he had a simalr problem, and made some suggestions. 

I found the "collar" on the tube loose, and the setscrew I though might 
have been arcing. I tightened it up, and looked over the inside of the PA 
with a magnifying glass. I could see no signs of arcing, so replaced the 
1 ohm resistor.

All was fine, until after a month or so of no use, I fired it up the 
other day. Ka-pow again. Sure enough, resistor was blown. This time I 
replaced the ,005 3KV bypass. Turned it on, all seemed fine for about 5 
minutes..then ka-pow again. Blew another 1 ohm resistor.

I can't see where it is arcing. I have a sinking feeling it might be the 
tube arcing internally. 

Anyone had similar experience steer me where to look next? Also, 
suggestions as to where to purchase an 8072 for the final, at the best 
price.

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+-++-++-++-++-+   John L. Sielke
|W||2||A||G||N|        http://www.w2agn.net
+-++-++-++-++-+    Ex-K3HLU,TF2WKT,W7JEF,W4MPC,N4JS