I'll agree with VK4TUZ on good experience with RF parts.? I needed 2 3-500Z tubes for a Heathkit HL-2200 basket case that I restored.? After looking far and wide, I found all sorts of price variations and warnings.
My take away form the research was this.? All these tubes at the time came from a couple Chinese factories.? Way to tell which factory was whether the base of the tube was brown or white.? Neither factory made quality tubes, but the brown base tubes seemed to have a lower failure rate.? RF Parts, Matchlett and Penta Labs were all using and rebranding the brown base tubes.
But the big issue was and still is: if you buy direct at low prices you get no assessment of the tube quality.? If you buy from the US based outlet of Matchlett, Penta Labs and RF Parts you get a pre tested tube that is guaranteed to be operational and carries a warranty.? Buying direct you get a "pig in a poke" that might be good or might be junk because it has never been tested.
Learned this the hard way trying to cheap out on a set of 811A's.? Bought direct and had a 50% out of the box failure.? Spent months trying to get replacements and eventually gave up.
After that, RF Parts became my go to source for power tubes.
ron
KA3JIJ
