Originally Posted by MartyStrat54

... I was over at your other place for a while, but thought that I would come over and talk about the BZ7. To me, it seems as if maybe the amp just doesn't like them installed permanently. Some circuits place different voltages on the BZ7 over what an AX7 would see. Since it has less plate resistance, maybe it is getting hotter than it should? However, in all of my old reference materials, a BZ7 is listed as a replacement/substitute for an AX7. Who am I to argue with all of these old books? The AX7 is a lot older tube than a BZ7. I don't think the BZ's were around until the early 60's.

One thing on EBAY that you see a lot. "SOLD AS IS/NO RETURNS." (This gives you a real secure feeling when placing that bid.) I guess I could send you another and if it goes bad, then it goes back to what I said a long time ago with BZ7 #1, "the amp doesn't like them." And I'd hate to see good tubes go bad if it is indeed the amp that is eating them. I'll let you make the call on this one....