<story><title>Reverse-engineering the waveform generator in a 1969 breadboard</title><url>https://www.righto.com/2022/03/reverse-engineering-waveform-generator.html</url></story><parent_chain></parent_chain><comment><author>bragr</author><text>I love the hand hewn charm of these old boards. Now even homemade boards are designed in software so everything is very straight and regular, but with old boards you can tell everything was done by hand from the design to the layout to the assembly. Don&amp;#x27;t get me wrong, it&amp;#x27;s great that you can cad something up, send the files off, and get perfect boards in 2 days, but these old boards are the electronic equivalent to a charming, rustic, cabin in the woods.</text></comment>
<story><title>Reverse-engineering the waveform generator in a 1969 breadboard</title><url>https://www.righto.com/2022/03/reverse-engineering-waveform-generator.html</url></story><parent_chain></parent_chain><comment><author>formerly_proven</author><text>&amp;gt; The sine-wave shaper appears to be inspired by the similar circuit in the HP 3300A Function Generator, introduced in 1965. The schematic below shows the HP 3300A&amp;#x27;s sine-wave shaper; the breadboard&amp;#x27;s network is similar. The resistances are carefully chosen to achieve the sine wave.&lt;p&gt;In some Philips FGs they had sine shaping ASICs (presumably with a ton of taps and good matching) and managed to get distortion down to 0.1 % iirc (which for the 70s or early 80s would have meant that you don&amp;#x27;t really need a proper RC oscillator any more for testing audio amplifiers).</text></comment>