[Amps] ceramic vs glass

[Col. Paul E. Cater]

I'm dubious about some of the ceramics. The ones that require more parts to
protect it then actually use it and the old Russian jobs.


 The 500Z is a time proven design. Many of the failures are do to
mechanical issues, over optimistic ops, and not the tube itself. I have
never understood why someone would build up a pair of 500s and put a muffin
fan on them. Cheap commercial jobs do this to save money. It is really a
disservice to the tube and it's capabilities. The mean time between
failures on muffin fan types and actual blowers with chimneys on these guys
is enormous.


 Paul

WD8OSU



On Sat, Jan 24, 2015 at 9:08 AM, Jim Thomson <jim.thom at telus.net> wrote:

> 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
>
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