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Re: [Amps] 3-500 to 4-250 conversion

To: "" <>
Subject: Re: [Amps] 3-500 to 4-250 conversion
From: Jim Garland <>
Date: Thu, 16 Feb 2012 08:29:05 -1000
List-post: <">>
Hi Kennon,
On the face of it, anyone who would build an amplifier using six 3-500zs, and 
then proceed to burn out all the tubes, pretty clearly wasn't knowledgable 
about the rudiments of power amplifier design. There's no way I can think of to 
make such an amplifier work on 10m, and probably not on any hf band above 160m, 
and maybe not even there. My advice is to scrap out the amp for the parts and 
turn elsewhere for advice about sound amplifier design practices.
Jim w8zr

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> Date: Wed, 15 Feb 2012 23:58:49 -0800
> From: kennon lewis <>
> Subject: [Amps] 3-500 to 4-250 tube conversion
> To:
> Message-ID:
>        <>
> Content-Type: text/plain; charset=ISO-8859-1
> hello. recently I received an amplifier with 6 bad 3-500z tubes in it. i
> have a bunch of good 4-250 and 4-400 tubes on hand and am looking to
> convert the amp to run on these tubes. the cost of purchasing 6 new 3-500
> tubes is out of the question at this time. the amp covers 10 - 80 meters.
> looking at the tube data it looks like all i need to do is strap pins 2 and
> three together with a low ohm resistor and that should do the job, one
> being a triode and the other a tetrode. the power supply seems more than
> adequate. any schematic help or other information will be greatly
> appreciated. thanks ke5rgm
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