My homebrew 3CX800 amplifier filament transformer started with a 3 amp 12
volt Radio Shack transformer. I did not have enough voltage so I simply
added a few turns and increased the voltage for the two tubes.
The transformer had lots of extra space on the windings and I did not even
have to remove the laminations. I simply carefully scramble wound about 10
more turns of #18 (could have been #20) enameled wire. Kept measuring the
voltage until I had what I needed.
The original windings were scramble wound too so no need for neatness with
my added windings.
73
Jim W7RY
----- Original Message -----
From: "robert briggs" <vk3zl@bigpond.com>
To: <amps@contesting.com>
Sent: Saturday, May 16, 2009 6:03 AM
Subject: [Amps] filament transformers
> You are right Carl...I have always had the roving eye at hamfests and
> disposal stores..I once brought 5 new Jennings vac variables, 5-500pf
> for one dollar each at a disposals place...When I took them to the
> counter and asked how much, the guy said $5 for the glass tubes....I
> nearly ran all the way home...
>
> It is a shame that a lot of the old arts of home brew are being lost
> these days..I know that many think that they don't have the ability but
> the fact for me has been necessity as many components are just not
> available in VK and too expensive to import..I still have a shed full of
> "treasures" which I have collected over the years and I regularly search
> through forgotten boxes of heaven knows what and old chassis looking for
> "that" part" to complete a project..
> I remember my first 80 meter transmitter crystal controlled...I pulled
> apart many old FT43 crystals and re ground them on a piece of glass with
> some bath cleaner, a painstaking job that many hams much older than me
> will remember well..That was about the time I started re winding old
> transformers and have been doing it since...You have to be inventive
> some of the time but I guess that is what gives us the satisfaction when
> you put something together and bring it to life...
>
> Ah well, I guess time moves on and things change....
>
> 73 all..Bob VK3ZL..
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>
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