Hello everyone I’m doing a distortion that uses two linear VCA based on OTA Lm13700 one to control the drive the other one to control the positive feedback, I used this design in many projects and always worked fine for what I needed, although on this particularly (the pcbs are smd) the lm13700 generates some weird pops And crackles and the signal looks like coming and going and the stabilising again and then disappearing and coming back in other words is working odd! Before starting to look deep into the problem do someone have an idea of what can cause this? I’ve checked voltages on all the pins and seems everything in order, all values are correct too. Attached a picture of the design drive cv stage (input seristors are 680ohm not 3k)
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Welcome! If it crackles then id apply flux and re-float the board. A single dry joint may be your issue.
Hey thanks for the help, although I’m afraid is a bit more then that, I’ve replaced 3 ics all do the same, it works intermittently, last one I’ve put worked fine for 1 hour and then started that again.
Can you post the rest of the schematic, Im curious about how you’re implementing positive feedback, I was thinking about some stability issue with the design though I tend to agree with @Farabide that it is more likely due to a poor connection somewhere in the actual physical construction of the circuitry than a design flaw.