[Amps] GI-7b issues

Robert Perdue kc0hfl at cox.net
Tue Sep 9 13:57:00 EDT 2008

Looking for any info on the GLA-1000 conversion to the GI-7b tube. I have done the w4emf conversion but I am having problems with the tubes self destructing. has anyone else had issues with this tube? The amp runs fine and then boom the tube melts down without any indications I have watched current draw very close and that seemed fine but the tube just fails with a pop it melts the solder out of the tube around the Anode cap. Could it go into oscillation causing this? And for some background I ran the filaments for 48 hours before use. I have got 4 more tubes ready to go again but would like to find the problem before proceeding. Anyone else having failures?

73, Bob kc0hfl  

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