-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of
Steve, NR4M
Sent: Friday, December 25, 2020 3:17 PM
To: Jim
Cc: amps@contesting.com; amps@groups.io
Subject: Re: [Amps] W8ZR Autotune Amplifier Progress Report
Good question. I was wondering the same thing.
Those switches have a serious detent.
Someone who has the resources could partially fill them in
with a machine able epoxy.
73 de Steve NR4M
Sent from my iPhone
On Dec 25, 2020, at 3:47 PM, Jim <jimw7ry@gmail.com> wrote:
Question Jim..
Do you (would you) remove the detent from a Radio Switch
band switch? Or will a large enough stepper turn them with
the detent in place?
Thanks
73
Jim W7RY
On 12/19/2020 3:33 PM, Jim Garland wrote:
Hi all,
As you probably know, commercial automatic vacuum tube
amplifiers have been available for more than decade, but they
are expensive; their pricetag adds about $2000 to the cost of
a comparable manual-tuned amplifier. For homebrewers,
autotune capability is complex and difficult to duplicate, at
least for most of us who are not professional design
engineers with access to sophisticated workshops. For the
past year, I've been working on an autotune control circuit
intended to overcome these barriers. The purpose is to make
it possible for amateurs with average technical skills to add
autotune capability to almost any vacuum tube linear
amplifier, whether homebrewed or commercial.
Here are the design goals for my controller:
(1) The performance should rival that of
top-of-the-line commercial autotune amplifiers, (My benchmark
is the Alpha 9500.)
(2) The controller should be easy to duplicate for
amplifier builders with average homebrew experience.
(3) The controller should be affordable, costing no
more than $100-$200.
It has taken me a year to realize these objectives, most
of which was spent learning to use an advanced, yet
inexpensive, microcontroller called the Propeller PX32A. (The
PX32A was designed in California by the Parallax Corporation,
maker of the popular Basic Stamp controllers) The PX32A is a
sophisticated device containing eight fully independent
32-bit microprocessors that share 31 read/write IO ports and
a common memory for storing variables, computation results
and data. These features make it possible to construct a
complete amplifier autotune circuit on an uncrowded file
card-sized printed circuit board using ordinary through-hole
components that can be wired up in an evening. The circuit
board intelligently operates inexpensive stepper motors and
motorized switches to adjust the tank circuits of almost any
h.f. vacuum tube amplifier. An ordinary PC or laptop computer
programs the device, but once programmed, no external
computer is required. Because of its power, the PX32A
implements numerous advanced features while requiring only a
handful of additional components.
Although it has taken me almost a year to write and debug
the program
code for this controller, I 'm finally ready to move the
project out
of the breadboard stage. Here's a link to a YouTube video that
demonstrates the controller's user features. (My eventual
amplifier
will use an 8877 triode in a conventional grounded grid
circuit, but
that's a topic for another day.) I apologize for the
crudeness of the
video, but hope you find it interesting and will let me know your
comments and suggestions. (If the below link doesn't work, just
Google "W8ZR YouTube Prototype Controller" )
https://www.youtube.com/watch?v=1qDGoEElKcU
Thanks and 73,
Jim W8ZR
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