I’ve build the Eddy Bergman’s stripboard layout of the Yusynth Steiner-parker VCF:
My build is not working correctly. The output is very faint, almost inaudible.
So far I looked for cold joints, wrong parts, continuity. I figured that for any further troubleshooting I need to have a better understanding of the circuit. To help myself with that, I partially created the circuit in the Fallstad circuit simulator. I can’t get it to work properly. Anyone care to take a look? https://tinyurl.com/2d4lamqu
Any help is really apreciated.
I will add some pictures later. But right now I was hoping that someone can take a look at the fallstad simulation. To get that correct.
By using the fallstad simulation i’m trying to get a better understanding of the circuit (and hopefully I’ll be able to ask more specific questions).
I’m sorry I can not help you with the Fallstad simulation. I have no idea how that stuff works. Sometimes people send me simulations of my projects and in that case I post them in the appropriate article but I don’t make those myself. As for the filter. It’s one of the simplest and at the same time one of the best sounding filters you can build. It should be relatively easy to troubleshoot if you compare you stripboard to the schematic. The layouts are verified. I built a few of these now and they all work fine. First rule of troubleshooting is: Thou shalt measure voltages. See if everything gets the required power. If you have a scope, trace the signal through the filter and see where it cuts out.
Measuring the voltages is what I’m actually trying. But to me all this stuff is new. And I’m unsure of what the voltages should be at several points. So I figured if I make a fallsstad simulation I could compare my measurements to that (and learning more about the circuit while doing it). It’s me trying to do the due diligence work.
Anyway, not getting the fallstad simulation to work is not a show-stopper. I’ll have to change my approach. I’ll try to do some measurements when I get the opportunity and post more later.
I think you’re overthinking the problem. Simply go over the layout with a fine toothed comb and check for errors. There must be an error somewhere because the layout works. Maybe there a cut that’s still conducting or a fault in the grounding.
Is everything powered correctly? I specifically check if all the IC’s get their +12 / -12 volts or whatever they need. Also check if ground is connected.
I check the conductivity. It is super easy to accidentally connect two adjacent strips with a bit of solder. I just go over them with a multimeter that beeps.
When this did not yield any results, I take a scope and I start from the inputs and trace the signal through the circuit. Most times, you have an idea of what you would like to see. In your case, there is probably a spot where the signal gets substantially weaker and thats where you need to dive a bit deeper.
Finally, I always prototype on a breadboard to see if I can get things working at all. There are faulty circuits to be found online though I believe this one is well tested The breadboarding will greatly help with understanding the circuit and has helped me countless times to debug & tune the actual build side-to-side with the breadboard. For example, when you have subtle problems, like noise or some resistor values that are off, it is very helpful to not have to desolder components and replace them (I hate doing that haha).
Yes it does get weaker there because it will be connected to R7, R8 or R12, which each go to GND, making a voltage divider.
Also be aware that with inverting opamps you can have no measurable signal at the inverting Input (pin 2 at IC1a) but still have the correct signal at the output.
As you guys pointed out I was really overthinking it. The 47uF cap cathode was connected to H45 instead of G45…
The past few weeks I’ve checked it so many times… and visually I thought it was all ok. Of course I was expecting that I made a mistake, or perhaps some defect component. I feel kinda silly asking for help knowing now what was wrong.
Thank you all for bearing with me.
I’m still going to try to get the simulation working. It’s bugging me why I can’t get it to work in Fallstad. It’s probably something silly. Anyway, I will post it here if I ever succeed. But first I’m going to play with my new Filter
Don’t know.
At the last opamp it’s outputting the max the opamp can output.
I’m suspecting I did something wrong with the transistors or maybe the resonance part or the circuit. Resulting in to high voltage that the opamp amplifies to its maximum.
Have you tested the opamp alone? I have this weird problem in falstad, that I can not use the opamp from the menu, I always need to open the opamp example file and start from there and then copying the one working opamp that I got from the start xD
