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Old 13th July 2014, 12:49 AM   #1
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Default Old School Prototyping

I have used wood as a building platform since I began building electronic circuits many years ago. It has always been and still is my favorite "media" for prototyping audio circuitry.
This photo is my latest circuit "board". It is an old circuit that (I believe) may be one of the first examples of the summing amplifier that is commonplace today in op amp designs. Back in 1968 it was unique enough to be granted a patent. I built the breadboard to be able to play around with the design to see what I could learn from it.
The board was built on cabinet grade plywood. I attach a copy of the schematic diagram printed to size to the plywood with "glue stick" adhesive. This works well since it is low moisture and doesn't wrinkle the paper. Then brass escutcheon brads are nailed into the wood at connection points for the circuit. Once the brads are in place (with about a half inch exposed) I wire the circuit using plated solid copper buss wire soldered to the brads. The brass solders easily. Once wiring is in place the components are soldered in.
Breadboards made this way are easy to experiment with. They can be made large enough to make trying different components an easy task. And they survive revisions very well.
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Last edited by mikegranger; 13th July 2014 at 12:52 AM. Reason: add photo
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Old 13th July 2014, 01:21 AM   #2
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I was brought up on strip board for prototypes.
It usually works ok.
I have had circuits fail and blow off the strip board tracks.

These days I usually go straight to pcb's from China.
It China pcbs cost 1/3 the price of what they do in the UK.
Obviously you need to get the circuit right if you go straight to pcb.
I sometimes knock up parts of the circuit I am unsure about on strip board before going to pcb.
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Old 14th July 2014, 03:38 PM   #3
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Quote:
Originally Posted by mikegranger View Post
I have used wood as a building platform since I began building electronic circuits many years ago. It has always been and still is my favorite "media" for prototyping audio circuitry.
This photo is my latest circuit "board". It is an old circuit that (I believe) may be one of the first examples of the summing amplifier that is commonplace today in op amp designs. Back in 1968 it was unique enough to be granted a patent. I built the breadboard to be able to play around with the design to see what I could learn from it.
The board was built on cabinet grade plywood. I attach a copy of the schematic diagram printed to size to the plywood with "glue stick" adhesive. This works well since it is low moisture and doesn't wrinkle the paper. Then brass escutcheon brads are nailed into the wood at connection points for the circuit. Once the brads are in place (with about a half inch exposed) I wire the circuit using plated solid copper buss wire soldered to the brads. The brass solders easily. Once wiring is in place the components are soldered in.
Breadboards made this way are easy to experiment with. They can be made large enough to make trying different components an easy task. And they survive revisions very well.
Hello mikegranger. I looked up your patent at United States Patent and Trademark Office. This is an interesting and practical approach to prototyping; highly worthy of adoption. Did you make money of your invention during the time OP amps [like uA709 and uA741] and their virtual ground applications may have competed with [or infringed on] your circuits?

Best regards
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Old 14th July 2014, 04:18 PM   #4
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Default Patent was not mine

Quote:
Originally Posted by Antoinel View Post
Hello mikegranger. I looked up your patent at United States Patent and Trademark Office. This is an interesting and practical approach to prototyping; highly worthy of adoption. Did you make money of your invention during the time OP amps [like uA709 and uA741] and their virtual ground applications may have competed with [or infringed on] your circuits?

Best regards
Antoniel,

The circuit I used to illustrate my wood prototyping does not belong to me. I built it to experiment with it to see what I could learn from its operation.
As you may have noticed the patent literature shows William Dilley as the inventor. He was a well respected designer of professional audio equipment used in studio And broadcasting. Your question is one that I have wondered myself. Thanks for your interest!
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Old 14th July 2014, 04:50 PM   #5
The Dastardly Dad of Three
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Fwiw I think this is really cool... Reminds me a little of a project that got me started in electronics
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Old 14th July 2014, 08:30 PM   #6
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Originally Posted by kasey197 View Post
Fwiw I think this is really cool... Reminds me a little of a project that got me started in electronics
Kasey197....
Your very cool circuit "board" brings back so many good memories. My first electronics endeavors were all radio related. I can' tell you how many I built before I got a project to actually work! I wish I still had some of those old projects.... I might know enough now to make them work! Thanks for sharing your circuit board with us. Am I right in thinking it is a two transistor AM receiver? What kind of transistors did you use?
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Old 15th July 2014, 03:00 AM   #7
The Dastardly Dad of Three
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Yes indeed that is was what it was. This was from a Ladybird book from the 70's popular in the GB and the commonwealth countries.

IIRC it used the mullard OC series germanium transistors that you could scrape the paint off and make a photosensitive transistor. At some point I could not find them anymore and was advised to use a metal can AC XXX can't recall which ones.

Somewhere on the web is an article describing this particular 'project' along with some improvements necessary for it to work reliably - it never did to my recollection !

The book is called Building a Transistor Radio.
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Old 15th July 2014, 02:19 PM   #8
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Quote:
Originally Posted by kasey197 View Post
Yes indeed that is was what it was. This was from a Ladybird book from the 70's popular in the GB and the commonwealth countries.

IIRC it used the mullard OC series germanium transistors that you could scrape the paint off and make a photosensitive transistor. At some point I could not find them anymore and was advised to use a metal can AC XXX can't recall which ones.

Somewhere on the web is an article describing this particular 'project' along with some improvements necessary for it to work reliably - it never did to my recollection !

The book is called Building a Transistor Radio.
Thank you for the information. I will look around and see if I can find the book or the web site you mentioned. By the way, it has occurred to me recently that most of the projects I built back in the early days were class A biased circuits. They sounded good and I never realized why!
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Old 15th July 2014, 05:09 PM   #9
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Kasey197:
I took A look around and found this:
MDS975 - "Making A Transistor Radio" by George Dobbs
It obtains the reprint of the book you mentioned as well as construction details to build the radio using the construction technique you used. Very nice. I appreciate your letting us know about this little gem.
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Old 16th July 2014, 02:17 AM   #10
The Dastardly Dad of Three
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yes thats the one!The same website has a lot of information on modern parts use and examples of builds. Have fun
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