[Amps] ceramic vs glass

[Jim Thomson]

Date: Sat, 24 Jan 2015 12:53:21 +1030
From: "Leigh Turner" <invertech at frontierisp.net.au>
To: "'Bill Turner'" <dezrat at outlook.com>, <amps at contesting.com>
Subject: Re: [Amps] 5 Minutes for Ameritron 811H to warm up?


Personally I wholeheartedly concur with your sentiments here Bill; most of
my shack amps are of the ceramic tube variety and indeed do seem to last
forever.

My only exception amp is the venerable Kenwood TL-922 with its nostalgic
pair of Eimac 3-500Z glass bottles...they too have proven very reliable
workhorses!  The proviso rider with any tube is absence of abuse.

73

Leigh
VK5KLT

##  whats the most anybody has gotten out of these russian ceramic wonder tubes
like GU-74B etc ??     Can you get 20 years out of them, beating on em 7 days a week,
like an Eimac 3-500Z  ?  

##  What is longest anybody has gotten out of an Eimac 8877 ?? 

##  at least with the bigger eimac ceramic tubes, like 3x3, 3x6, 3x10, 4x5, 4x10,
they can be re-built till hell freezes over, unlike their throw away, smaller ceramic
siblings.   IMO, you get a bigger bang for the $  with the bigger ceramic tubes, esp
since being thoriated tungsten fil, you can reduce the fil V way down, like 12% or more,
further extending tube life.   Take a 3x3... rated for 2.5 A  CCS plate current...then run it
at 1.5 to 1.7 A plate current..alon with reduced fil V.  It will last forever.  
The typ 2 x 3-500Z amp is rated at 800ma max plate current.... and my L4B runs
at 800ma..just to get 1290w po. 

Jim  VE7RF