Let's amp up the discussion on OpAmps (Operational Amplifiers) and how they work

[james]

RadioShack had spec papers on the chips they sold. They also had project books that used the chips. I was always impressed by the equivalent circuit of an op-amp drawn using discrete transistors. There's a lot going on in there!

[JohnYayas]

Real men use mag amps.

[laserist]

Real men use mag amps.

Really old men...

[lasermaster1977]

Really old men...

Or their name is McIntosh...

[laserist]

Or their name is McIntosh...

My apologies if I got your comment wrong...

https://www.righto.com/2012/02/apple...power.html?m=1

[lasermaster1977]

My apologies if I got your comment wrong...

https://www.righto.com/2012/02/apple...power.html?m=1

It was my mistake, I thought I was replying to JohnYayas comment.

Great article though!

[lasermaster1977]

Gone are the days of being able to walk in to RadioShack, Olson's, Phil-Cap, etc... and buy op-amps and other electronic bits to make homebrew gear. I used to know all the people who worked in those places and had many great conversations.

That made something "click" when you mentioned RadioShack being a source of electronic bits. Most of their stuff was cheap but serviceable as I recall and they were one of the few sources for DIY "learning opportunities" in electronics.

Like HankLloydRight mentioned Dynaco kits. My dad built a Dynaco stereo phono pre-amp from one of their kits. I remember watching him and thinking...so this is how stuff like this is made! From 1970-'75 I became a big fan of Heathkit stuff, building their Audio Oscillator, Transistor Curve-Tracer (which I still have and still works), Dual-Trace Oscilloscope, TV Color Bar and Sweep Generator.

Well, back to Radio Shack. Around 1974 I wanted and needed IC based mic pre-amps and learned about the uA739 dual, low-noise op-amp. I think I took the circuit design from Fairchild's app note. Radio Shack sold what was kind of crude DIY PCB prototyping kits consisting of a 3" x 3", 1 oz. light sensitive copper clad board, one sided, some 2-layer, red photo masking material and some small bottle liquids. With an X-acto knife you cut out the red overlay material where you did not want any copper traces, leaving the clear acetate substrate material. Using darkroom techniques, in the dark you clamped the red photo masking material onto the circuit board then exposed the pcb to light for so many minutes, then dunked the board in etching solution, neutralizer and rinsing solution.

Here are photos of this Radio Shack enabled, DIY effort of mine. And it worked! I never could find a matching edge connector for it since I just made it up on the "fly" at the time.

[james]

That's neat! I made my own single sided circuit board with a special magic marker that was a mask for the etching solution. I built the Heathkit guitar amp. That was really neat. My dad had an entire ham radio setup with a transceiver, a wide band spectrum scope display a high power rf amplifier and lots of other stuff from Heathkit. I made audio stuff like electronic guitar modifications, mic preamps, mixers, distortion effects etc... as part of my recording equipment for when I recorded my own original CD. It's amazing how good a super cheap electret capsule mic can sound. I used to buy them by the hand full at hamfests. I also built my first computer, the Sinclair ZX81, from a kit.




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[james]

Real men use mag amps.

Back in 1986, I worked for the Summer at Empire Detroit Steel in Mansfield Ohio. I worked in the hot strip where they rolled either ingots or slabs into coiled sheet steel, 12 to 25 tons each. After the blooming mill and the edger did much of the work of rolling the large chunk to a much thinner and longer piece, it went through the reduction rollers to get it to a precise thickness. Each reduction made the sheet longer and the convener rollers had to all be precisely controlled for the relative speed needed to keep it all moving without it binding up. All the roller motors were AC synchronous and each stage was directly driven by sine wave oscillators with huge high current tube amplifiers (hundreds of 6L6GC power amp tubes) providing the power to the motors.

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[HankLloydRight]

. Radio Shack sold what was kind of crude DIY PCB prototyping kits consisting of a 3" x 3", 1 oz. light sensitive copper clad board, one sided, some 2-layer, red photo masking material and some small bottle liquids. With an X-acto knife you cut out the red overlay material where you did not want any copper traces, leaving the clear acetate substrate material. Using darkroom techniques, in the dark you clamped the red photo masking material onto the circuit board then exposed the pcb to light for so many minutes, then dunked the board in etching solution, neutralizer and rinsing solution.

In high-school (1981 or so) I bought a box of old Popular Electronics magazines at a local electronics/ham radio auction. I read every page of every issue (probably about 3 years worth). And one of those issues had a small laser project on the cover that I *always* wanted to build, but we were pretty poor and I could never afford the parts for that.

Anyway, one of the other projects was an electronic fishtank heater, and having my own fishtank at the time, this was the perfect project.

I didn't have the red tape, but instead I used a silk-screen in the HS art shop to mask the copper board (I hand drew the traces--it was pretty ugly!). Then exposed that to light and etched the copper. And it worked! The only problem at the time was the heater was a buss of about 20 resistors and the project called for encapsulating it in "epoxy potting compound". I searched for months to find this material but never could find it. Now I know what it is, but back in 1981 and no internet, I was out of luck. So in desperation I just used regular epoxy which was much more messier, but I finally got it coated. I don't remember if I ever put it into service in my tank, I think I was too afraid of electrocuting my fish.

I still have it around here somewhere.