Have you tried to trace the input signal through the various stages and checked what happened to it? This may lead to you finding where it is lost in the circuit.
B.t.w. did you start your invenstigation by checking the power supply voltages of the ICs?
Now I have a VCH - voltage controlled heater! I was replacing a suspect resistor and the soldering iron tip shorted -12v to the TL074 output. I stupidly put in another one… oops that was my last TL074.
Now I’ll have to wait for Tayda 
Lesson learned - check voltages before plugging in your last chip.
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HARDCORE NECRO! because I’d rather necro and create a single resource than start a new post 
OK SO I just built my MS-20 filter to what I thought was perfection but instead of a filter I built a constantly maxxed out screaming self-oscillating resonator!
The cutoff knob works as frequency/pitch which is understandable but the cv input and the cv pot don’t make any change, and the resonance knob kind of seems like it might be changing something sometimes but it’s definitely not the resonance!. The input seems to do something to the sound, kind of barely. it mostly just intermittently cuts the resonance for a split second.
I’ve checked the jacks and pots and they are TECHNICALLY connected properly so I’m assuming I made a mistake elsewhere. I’m going through manually tracing the circuit in its entirety but any help would be appreciated!
I guess just as an update to my issues, I realized that in the stripboard layout it shows CV in/cv level pot/resonance pot ground all connected to each other and nothing else. I was connecting it to ground. I disconnected that and I feel like that’s what fixed the max resonance issue, but in the notes it seems like it’s supposed to be connected to ground. Even after disconnecting those my CV input and resonance don’t do anything at all, but at least the cutoff knob works now.
I’ve double checked my circuit against the stripboard layout like twice and still can’t find anything although I don’t know how this thing works well enough to target my efforts. Any help would be greatly appreciated.
Also if there’s a thread dedicated to this please let me know!
The black wire on the pots should be connected to ground. See the note near the bottom. Also the other terminal on the input jack should connect to ground.
See:
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Thanks for the info. I ended up hooking back up the ground. Still having max resonance issue but I set the project aside to work on a few other modules. When I get back to it I will follow your troubleshooting advice.
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