Hi Brach, sorry for the late reply, I was out of town for a few days.
I just checked the pots, they all seem to be fine, going from 0 to 5V, except for th Volume pot, which doesn’t show any voltage. Still working though, so that’s probably fine.
Both LDRs show a resistance of 1,8M in complete darkness. I taped black tape across it, and even shining a light directly onto them didn’t affect it. So I can safely say that they are not leaky.
I attached a video that shows how the LEDs behave depending on the position of the mix dial. It seems inconsistent. One would assume that both LEDs would work in the same but opposite way. But while the low LED flashes on the “low” side of the dial, and goes steady towards “hi”, the high LED only flashes in the middle position, goes steady in the dark position, and goes completely dark when the dial is all the way at “hi”. Sometimes it’s on though, when on “hi”, sometimes it’s not, so that’s another weirdness. So either it’s (from lo to hi) stead-flashing-off, or sometimes it’s steady-flashing-steady.
I tested for bad solder joints but so far I couldn’t determine what makes it go steady or of when the dial is on “hi” position.
http://www.falckenberg.com/downloads/Quaverato/IMG_8773.MOV
http://www.falckenberg.com/downloads/Quaverato/IMG_8775.MOV
Also, in one of the previous videos I showed the erratic behaviour of two pots. Could this be caused by some other fault somewhere else in the circuit? Measuring their voltage seemed fine, no erratic jumps, but as shown in the video they don’t behave that way.
This is getting frustrating 🙁
I could redo the optocoupler, or use a readymade one (I happen to have a silonex nsl-32 and a VTL5C2 lying around somewhere. Could any of these work instead?), but I have a feeling that won’t help, as they seem to be fine by the looks of it. The fault has to be elsewhere…
Could the TL074 be the culprit? Just asking, because it’s soldered in without a socket, so maybe it got too hot. I did take great care not to overheat it, but one never knows… Or the microcontroller? If this thing controls the optocouplers, maybe it’s faulty.