Rich Measures wrote:>
> ? If you purchase a 3-500Z and you would like to test it for defective
> anode-cooler spotwelds, slap the tube firmly into the palm of your hand a
> few times. The deceleration force thereby produced tests the strength of
> the anode welds. If the anode cooler tilts from the impact, it has
> defective welds. . . I performed this test on two Chinese tubes and on
> two Eimac tubes produced in California in the 1970s. None of the anodes
> bent. Out of five tubes produced at Eimac's SLC plant, four proved to
> have defective spotwelds.
> - Bad spotwelds can be spotted by inspection. If the spotweld-craters
> appear ragged, they are probably good. If the craters are clean and
> smooth, the welds are probably defective.
> - later
>
> Rich...
Talk about timely information...I just received two Eimac 3-500's, one of which
was said to be "questionable--works sometimes, other times seems like it may
have a short". Date codes 1987.
Inspecting them, I noted that one had the anode cooler bent in, well toward the
grid structure, in fact VERY close to it. I rotated the tube until the bent
plate structure was UP, then slapped the tube down, not too gently, into my
other hand. The structure at that point was almost perfectly straight, and
another gentle slap adjusted it perfectly.
Looking over the other tube, I noted it was slightly bent, and it responded
exactly the same.
A third 3-500z , non-Eimac had no such problem and a bit of gentle slapping
produced none.
I failed to note any spotweld, rather had assumed that the pin from the plate
cape to the internal plate structure was made of too soft material
and was actually bending. Evidently that is wrong.
Now the question:::::
Will these Eimacs, with plate structures properly aligned, perform properly? Or
will this "broken spotweld" problem render them useless? The fellow I got these
from, whom I believe, stated they both worked full output, with the caveat on
the one - that "sometimes shows a problem and isn't presented as being OK".
73, Dick W0EX
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