[Amps] W8ZR Autotune Amplifier Progress Report

[Jim]

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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