# Test AS3340 and TL072

**URL:** <https://lookmumnocomputer.discourse.group/t/test-as3340-and-tl072/1209>\
**Category:** KOSMO MODULES\
**Created:** [June 13, 2020, 12:47pm UTC](https://lookmumnocomputer.discourse.group/t/test-as3340-and-tl072/1209 "2020-06-13T12:47:26Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![fredrik](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/fredrik/32/682_2.png) [@fredrik](https://lookmumnocomputer.discourse.group/u/fredrik)\
**Post date:** [June 14, 2020, 7:23pm UTC](https://lookmumnocomputer.discourse.group/t/test-as3340-and-tl072/1209/15 "2020-06-14T19:23:27Z")

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Wait, 0 V from the tuning potentiometer too? You’d need a bit over 3.3 V to hit midi note 0 and about 5 V to hit the lowest note on a piano, so if you don’t get any voltage from the tuning pot at all, your keyboard may have trouble getting something useful out of the oscillator. Double-check how the tuning pot(s) are wired up.

But this could just be that the 3340 is fried; if the summing node is completely dead and your tuning pot is wired up in series with the 100k instead of as a voltage divider (see [here](https://lookmumnocomputer.discourse.group/t/cem3340-as3340-pot-question/602/15) for some discussion of various way to wire it), the current has nowhere to go.

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