Urban legend and a few old hands have it that the 3-500Z is the
exception - the anode has the getter material.
Since all the newer-style ceramic triodes most certainly do have the
getter in the cathode, (and assuming the legend is true) I wonder if the
difference has to do with design age or glass vs ceramic/metal? It
would be interesting to know if where the getter gets in a 4-1000A or
3-1000.
73,
Jim, N7CXI
On 7/20/2011 11:01 AM, kingwood wrote:
> Greetings to all,
>
> As I recall, EIMAC' s "Care and Feeding of Power Grid Tubes" says
> that the getter material, if any at all, is in the cathode (filament) of the
> tube, not the anode. It is the heating of the filament, containing the
> getter material, that causes internal gas to be ionized, emulsified, and
> bonded back into the metal of the anode (plate) of the tube. This is why an
> operator can "burn" the gas out of an EIMAC tube, but can not, in tubes like
> the Penta Labs PL-172, which has no getter material.
>
> With this in mind, the color of the anode (plate) of the tube has
> nothing, or very little, to do with "getter action", but rather the thermal
> reaction of the metal in the anode to heat. Of course they run with color,
> when ran any near their rated plate dissipation.
>
> Also, every tube chart I have looked at (note I did not say all)
> shows that third, and fifth, order IMD is better (less) with higher anode
> voltages. That is why most amp manufacturers recommend that their amps be
> operated with the highest anode voltage offered when operating in SSB.
>
> Lon W. Cottingham
>
> 1110 Golden Bear Ln.
> Kingwood, TX 77339
>
> 281-358-4207
> 281-795-1335 Cell
>
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>
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