>
>
>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.
>
? yes.
>Now the question:::::
>
>Will these Eimacs, with plate structures properly aligned, perform
>properly? Or>will this "broken spotweld" problem render them useless?
? With the repetitive heating/cooling expansive stress from ordinary
use, the defective welds tend to fail completely, and the anode cooler
falls against the grid. A number of owners of 3-500Zs produced at the
SLC facility reportedly experienced this problem when a tube was just
beyond the 12 month warranty period. From a business standpoint, the
anode-cooler weld situation was near perfect for selling more product.
- later, Dick
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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