>Not sure about the 3-500ZG designation but I am referring to the
>graphite plate 3-500s.
>
>My friend, WA4VWR, needs to replace a 3-500Z in his SB-220. He doesn't
>believe he should just replace one single 3-500Z with a 3-500ZG...
True - - so buy one Eimac - they are currently made by Triton/GE.
>... but
>he wants to know, if he replaces both of his Eimac 3-500Zs with the
>3-500ZGs, will he get less than, the same as, or more rf output
the same. He would get the same rf output if he replaced the 3-500Zs
with 3-400Zs because the peak emission is identical.
>with the exact same driving power?
Eimac 3-500Zs have slightly less Mu than other 3-500Zs. With a higher Mu
tube, the driving power needed is slightly less and the peak cathode
emission, and peak output, are identical.
>It's a good question that I certainly
>didn't have the background to answer.
The higher Mu version requires slightly more operate-bias to hold down
the ZSAC to the recommended 75mA per anode. At 3kV an Eimac 3-500z needs
about 5v of bias. Other brands need about 0v of bias.
>Is there someone out there that may have replaced the 3-500Zs in a SB-220.
I put higher Mu (Amperex) tubes in mine. I had to short out the zener
bias diode to get the ZSAC up into the linear region.
>or a Drake L4B that can answer the question for him.
>
>Also, (on my own), is there only a single graphite-plate 3-500 manufacturer
no
>and, if there is more than one, which one has the best reputation/track
>record?
seemingly Amperex.
Rich---
R. L. Measures, 805-386-3734, AG6K
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