On Apr 30, 2006, at 11:36 AM, Merv Schweigert wrote:
> I recently bought a pair of supposedly new Amperex 3-400z type
> tubes. Do these type require more drive than Eimacs?
Slightly less because the Mu is 190 instead of 130. Because of more
Mu, less cathode-grid potential is needed to achieve the same anode
current, and that takes fewer watts.
> I have
> tried them and they seem to have about the same output but take
> more drive and grid current to produce it.
The input Z of Amperex 3-400Zs is lower than Eimacs because the Mu is
higher in the Amperex version. Thus, there may be more input SWR
using Amperex in an amplifier whose tuned inputs were designed for Mu
= 130 3-500s, and higher SWR can reduce effective drive P.
> Also the idling current
> is less than Eimacs.
The Amperex 3-400Zs in my SB-220 require 0V bias for a ZSAC of 180mA.
> Sorry if this has been covered before, I just
> subscribed to the list.
> Thanks 73 Merv K9FD/KH6
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R L MEASURES, AG6K. 805-386-3734
r@somis.org
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