# Simple 1v/oct VCO Issues

**URL:** <https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504>\
**Category:** DIY STUFF\
**Created:** [July 26, 2020, 12:09am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504 "2020-07-26T00:09:43Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![F97](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@F97](https://lookmumnocomputer.discourse.group/u/F97)\
**Post date:** [July 26, 2020, 12:09am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/1 "2020-07-26T00:09:43Z")

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I have recently build the CEM3340 based simple VCO with the full square wave modifications. After making and fixing a few mistakes, its behaving very oddly. The wave shaping for the triangle and saw waves is working, but rather than a tone its giving out a screeching sound, reminiscent of dial up. The tuning knob and CV input are not changing the pitch of this screeching, even though they are (to my knowledge) wired correctly. I am also getting no output at all from the square wave. Any help would be greatly appreciated!

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**Author:** ![Dud](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/dud/32/610_2.png) [@Dud](https://lookmumnocomputer.discourse.group/u/Dud)\
**Post date:** [July 26, 2020, 10:46am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/2 "2020-07-26T10:46:40Z")

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wecome @F97

this one ?

 ![CEM+3340+PWMFIXED](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/0/078ea2710d1718529f7ef861816cac796194c3e1.jpeg)

maybe check and check again all connections, components and solder

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**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\
**Post date:** [July 26, 2020, 1:55pm UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/3 "2020-07-26T13:55:59Z")

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you say the wave shaping for the saw and tri are working, but give out screech… so that’s contradictory.

Without knowing the circuit or and hi-res images of the build, its going to be difficult to give any advice.

post up what you have.

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**Author:** ![F97](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@F97](https://lookmumnocomputer.discourse.group/u/F97)\
**Post date:** [July 27, 2020, 2:17am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/4 "2020-07-27T02:17:27Z")

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![20200726_170401](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/4/4c6a888afa23c95c1e6dbb3c263fd9364dc9cd45.jpeg) ![20200726_170333](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/a/ac695b05200fffe9b288a0595f80b460bc0f2408.jpeg)

Here are images of what I’ve made so far. I’m having difficulties uploading a video of what it sounds like, but the noise coming from the triangle and saw outputs are distinctly different. It almost seems like its oscillating at a very high frequency, but I’m unable to adjust it.

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**Author:** ![ChristianBloch](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/christianbloch/32/56_2.png) [@ChristianBloch](https://lookmumnocomputer.discourse.group/u/ChristianBloch)\
**Post date:** [July 27, 2020, 2:30am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/5 "2020-07-27T02:30:01Z")

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Can we see the underside, please?

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**Author:** ![F97](https://avatars.discourse-cdn.com/v4/letter/f/8baadc/32.png) [@F97](https://lookmumnocomputer.discourse.group/u/F97)\
**Post date:** [July 27, 2020, 2:51am UTC](https://lookmumnocomputer.discourse.group/t/simple-1v-oct-vco-issues/1504/6 "2020-07-27T02:51:14Z")

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![20200726_224847](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/3/353031734539d6e369b3c1efe5cda7c0649cf232.jpeg)  
Here’s the underside of the board (some parts I had soldered into the wrong place, I have fixed all the ones that I was able to find). I wouldnt be too suprised if this is the result of cheap Chinese stripboard. Out of the ten I got this was one of the least disgusting.