Aren't all 3-400Zs now 30+ years old? -WB2WIK/6
> Question:
>
> I was given a homebrew single 3-400Z amplifier which works but I noticed
> with ZSAC the top of the glass envelope has a very faint blue hue when
> looking across the top of the tube envelope. When looking down at the top
> of the tube I don't see this color, only when looking across the top -
> keying CW does not pulsate the color, the blue hue is the same regardless
> of output power. I have a couple other old junk clunker 3-400Zs that do
> the same.
>
> Is this normal or is it an indication of gas?
>
> I have some 8163 Amperex 3-400Z in a Drake L4 that do not exhibit this
> coloration, ever. The Eimac 3-400Z tubes do, even after having been used
> to produce enough output RF to turn the anode reddish-orange for 10-15
> seconds. Or does the getter not getter that quickly...
>
>
>
> thanks
>
> 73 Jason N1SU
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