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[AMPS] Re: Tube chimneys

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Subject: [AMPS] Re: Tube chimneys
From: (YO3CTK)
Date: Tue, 10 Mar 1998 11:13:31 +0200
Frank, W2FCA wrote:

        Got a question about do it yourself chimneys. Having determined that
        oil cap will do just fine in my power supply, I'm now setting my
        on the amplifiers that it will power. I have a Svetlana 4CX800 and
        that I'm planning on using on 6 meters. 

        Hi Frank and all,

        I've almost missed your post in all that junk today !

        Referring to your question, I've done several chimneys for exactly
the same tube you have. A couple were made of a plastic which is locally
called "Duramid". I don't know exactly the chemical composition, but I can
find it if you're really interested. Anyway, it's flame-proof, heat-proof
and good insulator. Easy to machine it, too. But the chimney doesn't need to
be round, you know. For my current project (HF amplifier with a pair of
4CX800A) I'm using a "plenum" in form of a prismatic box made from
glass-epoxy PC Board stock (without the copper, of course). Just cut one or
two round holes 2.8 in dia. into the upper part and the anode(s) will fit
nicely. The box itself should be abt. 2 in high, depending on how you will
install the socket(s) . To assemble the box, you should prepare four square
columns, made of plastic material, also abt. 2 in long, with tapered holes
on two adjacent long surfaces and one tapered hole on the top and bottom
square surface. Then you can simply screw all glass-epoxy sheets in place in
order to assemble the box. The bottom hole in each column will be used to
fasten the box to the chassis. It's easy and straightforward, and if
carefully done you doesn't even need to worry about hermetically sealing the
box, which anyway can be done with epoxy cement.

        I'm not sure that this explanation is clear enough. Maybe my English
is not as good as I thought. If needed, I will prepare a drawing and send it
via E-mail. So please let me know. Good luck with your project !

        73 de Mike, YO3CTK

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