# As3340 vco tuning problem

I have a specific question when it comes to calibrating the alfa4 vco which uses the as3340 chip. So I’ve been trying to calibrate the module by say turning the coarse tune knob to say 130hz which is around the 10-11 o clock position on the potentiometer, then apply 1v and use the trimmer to adjust it to 261hz. Apply 0v and turn the coarse tune and adjust it back to 130hz. Rinse and repeat. Problem is that on the potentiometer, 130hz is around the 7-8 o clock position so as I do it and go lower, I eventually hit a point where I can’t adjust the coarse tune because it already reached it’s limit on the pot. So is there a way to somehow shift the 130hz to another position on the potentiometer or even reset the module entirely? This is the best way I can explain the problem and hopefully there is a way to solve this.

Coincidentally this video came up in my RSS feed this morning:

Don’t know if that helps or not, but the main point is: There’s no need to retune back to 130 Hz. Just go back and forth between 0 V and 1 V (or maybe 0 V and 3 V, as in the video) and regardless what the frequency at 0 V is, just notice what it is at both voltages, see if they are more or less than 1 octave (or 3) apart, and adjust the trimmer. If that gets you closer to 1 V/oct, good, if not, adjust the other way. Keep going until the two frequencies, whatever they are, are an octave (or 3) apart. (Confusingly, it can be that if the high note is less than an octave above the low note, you’ll need to adjust it lower, because that also adjusts the bottom note lower and maybe by a larger amount.)

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Oh yeah I have seen that video and it did help a lot with calibrating the other vcos and was helpful! But I did actually figure our how to basically “reset” it where I replaced the 1nf capacitor on pin 11 and 12 for a higher value (that being 10nf) and was able to finally calibrate it properly from there. But still I really appreciate the help and recommended video!

And if you want to be able to go even lower, you can also connected pin 1 of the Tune potentiometer to GND or even to -12V.