Moritz Klein Simple sample and hold

I built this module and it seemed to work fine on breadboard. When I put it on strip board I could only seem to get it to take the gate signal from my LFO if I wired it straight into the non-inverting input on the op amp. Even then it was acting strangely but not terribly. LOL. For some reason running it through the wave shaper will not work at all. I tried it again on the breadboard and I got the same result. I’ve had similar issues with other circuits working on breadboard then not working at all. The gate I’m using is around 7 volts + and -. Would it help if I put resistance between the non-inverting and the output on the op amp? I’m wondering if my gate just doesn’t have enough power…

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I’ve decided to do some experiments and just managed to “fix” the problem. Lol. I switched out the 1nf cap at the gate input for a 10nf and placed it where the diode was, and placed the diode where the cap was. Traded places. Now it works just fine. Great super simple module all together!

I don’t really understand the point of that diode anyway. The comparator threshold is positive (12*33/133 = 3 V) so anything negative isn’t going to affect it. All I can see it doing is it reduces the input voltage. Unless the op amp is single supply, then maybe the diode makes sense as protection. I haven’t watched the video but I’m guessing that isn’t the case.

In the original the RC time is 1 nF*(100k+100k) = 200 µs. In your modification the RC time is 10 nF*100k = 1 ms. I have no idea why it would work on breadboard and not on stripboard, but presumably the 5x longer trigger pulse overcame whatever it was.

I’ve had other similar experiences with breadboard testing. I have success with the test then I solder a strip board that doesn’t work as intended or even at all. I then move back to the breadboard to troubleshoot and then THAT circuit may or may not work…in this case the breadboard no longer worked right either. You’ve helped me with this type of problem before. I just got lucky and managed to guess in the right direction this time. I don’t like to give up either. I am persistent. Thanks for having a look at it. It’s a super neat module. I never even used a SH before. Im gonna build that YASH too.