# 3340 VCO problems

**URL:** <https://lookmumnocomputer.discourse.group/t/3340-vco-problems/3536>\
**Category:** DIY STUFF\
**Created:** [May 21, 2021, 4:17pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-problems/3536 "2021-05-21T16:17:45Z")\
**Posts on this page:** 1\
**Showing post:** 7

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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:** [May 21, 2021, 8:29pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-problems/3536/7 "2021-05-21T20:29:57Z")

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Pin 15 (CV) is a summing node and is held near 0 V by the 3340. To measure the CV, measure the voltages on the other side of the summing resistors, and add them together. See the “measure CV here” annotation in [the drawing](https://lookmumnocomputer.discourse.group/t/annotated-simple-1v-oct-oscillator-stripboard/1267), and [comment #3](https://lookmumnocomputer.discourse.group/t/annotated-simple-1v-oct-oscillator-stripboard/1267/3) in that thread. You need around 6 V to get an audible frequency.

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