[Amps] W8ZR Autotune Amplifier Progress Report

Fri Dec 25 17:57:49 EST 2020

CORRECTION to my spelling mistakes below.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 12/25/20 4:55 PM, Jeff Blaine wrote:
> I have an 86 in one of my tube amps.  A dual section type. Pulled out 
> the detent and use a type 23 direct drive.  Works great; way way more 
> torque than needed.
>
> The bigger issue (at least in my thinking) is the method you use to 
> determine the switch position.   I used a small belt-driven gear off 
> the switch over to a multi-turn pot which is _read_ by an _ADC_.
>
> The disclaimer to this is that Jim's build and design quality is way 
> way way better than mine.  So I'm only answering the "can it be done 
> that way" question.  Not the "yes, I know it CAN be done that way, but 
> SHOULD it be done that way?" question...
>
> 73/jeff/ac0c
> alpha-charlie-zero-charlie
> www.ac0c.com
>
>
> On 12/25/20 3:34 PM, Gary Schafer wrote:
>> I have a switch like that on an old TMC amp. It was very hard to turn 
>> to change bands so I put a much weaker spring on it and it turns very 
>> easy now. There is a micro switch that gets activated whenever the 
>> switch is properly aligned in each detent. I wired that micro switch 
>> in series with the PTT line so that you can only transmit when the 
>> band switch is precisely set on the proper band. Works great.
>>
>> 73
>> Gary K4FMX
>>
>>> -----Original Message-----
>>> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of
>>> Steve, NR4M
>>> Sent: Friday, December 25, 2020 3:17 PM
>>> To: Jim
>>> Cc: amps at contesting.com; amps at 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 at 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
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps at contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps at contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>> _______________________________________________
>> Amps mailing list
>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps