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[AMPS] Making tubes

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Subject: [AMPS] Making tubes
From: (Bob Marston)
Date: Thu, 05 Jul 2001 23:18:03 -0700
Billy Ward wrote:

> With the high price of tubes, I was wondering if anyone invisioned a
homebrew to actually make the tube from scratch ?

Let me answer the last part first.  Billy the start up costs involved in
designing and manufacturing a transmitting size tube is astronomical.
Remember you're not dealing with a light bulb here. Some of the respondants
to your post have touched on the quality control aspects of manufacturing.
The costs involved with R&D are several orders of magnitude higher. Pure
and simple Billy there is no need to reinvent the wheel.

There are ways to reduce the cost involved with amplifier construction.
First what must be realized that even as expensive as Eimac tubes can be
the bottles still only represent a fraction of the cost. For that matter if
anyone out there is looking to build a single amp with the intent of saving
gobs of money over a commercial amp they are badly mistaken. If you stay at
it long enough you will find techniques to reduce costs. One that
immediately comes to mind is to use a "pull" during the construction and
shake out phase. Say you were to design a single 8877. A "Pull"  would set
you back $350. If you were to suffer a parastic that blew the tube you
would be able to recover a few shuckles of its value by selling the dud to
Rich AG6K. Then after everything is cleaned up you could purchase a brand
new tube.  Another hint  Always start off simple. Build a monoband triode
amp first. For HF start out on 20 Meters. Then as you gain experience move
to multiband and then tetrode designs. After that head to vhf and then
cavity amps.

And lets not forget that Russian Tubes can be obtained for 1/3 to 1/5 of
the cost of their Eimac counterpart.

Stay Safe and Happy Building


Bob K1TA

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