# Troubleshooting First Build - CEM3340/Simple 1v/oct VCO **URL:** \ **Category:** DIY STUFF\ **Created:** [November 8, 2020, 6:23pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256 "2020-11-08T18:23:33Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [November 8, 2020, 6:23pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/1 "2020-11-08T18:23:33Z")
Hello, I’m working on my first project, Sam’s Simple VCO design with the CEM3340 IC, and hoping to get some troubleshooting tips from experienced builders. I’ve built the core module, and not having success with getting an output signal. I don’t have a VCA yet, so I’m running it through an interface to amplify (Fast Track C600), but only hearing a noise floor. Any ideas what might be causing this issue? I’m assuming there’s an oversight somewhere on my part. Much appreciated. Things I have checked: - Resistor/capacitor values - Continuity testing of stripboard connections w/multimeter - Confirmed appropriate power voltages of +/- 12v w/multimeter - I also tried using it with an ES-9 interface ![IMG_2772](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/9/98f1b0c21e4abab2149c0abad60ec02bb923985d.jpeg) ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [November 8, 2020, 6:24pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/2 "2020-11-08T18:24:35Z")
![IMG_2771](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/7/72f2325800ded8c807f7cd1730cf9c6ed3f80905.jpeg) ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [November 8, 2020, 6:25pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/3 "2020-11-08T18:25:07Z")
![IMG_2773](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/df062f5c05e51b99387feea6a5641053bfeda422.jpeg) ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [November 8, 2020, 6:25pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/4 "2020-11-08T18:25:39Z")
![IMG_2776](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/e/e32f0094124e68945521847920b2155a018df759.jpeg) ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [November 8, 2020, 6:39pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/5 "2020-11-08T18:39:49Z")
See this topic, it’s written for the 1222 PCB version but a lot applies also to the simple stripboard version. > [@Advice for troubleshooting 3340 based VCO](https://lookmumnocomputer.discourse.group/t/advice-for-troubleshooting-the-1222-performance-vco/2077): > > This is a wiki post; please correct and improve! This is written regarding the 1222 Performance Oscillator module, but similar things apply to the simple stripboard oscillator or other oscillators based on the 3340 chip. For the stripboard version also see If you are not getting good tones from the oscillator, do the following. If with the 1222 you are also not getting good behavior from the tuner, don’t waste time on trying to fix that yet. Get good tones on the outputs first — the tuner won… In particular, check voltages on the right sides of the two 100k resistors. ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [November 8, 2020, 6:43pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/6 "2020-11-08T18:43:54Z")
This is a great resource, I’ll start there. Thanks! ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [March 21, 2021, 6:30pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/7 "2021-03-21T18:30:17Z")
Update: it’s been a process of debugging and learning lessons on the fly, but It’s finished and working. Thanks for the help! ![IMG_3672](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/5/54dec62182c6429240d5ebe1d718bac8799fe11e.jpeg) ---
**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:** [March 21, 2021, 7:32pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/8 "2021-03-21T19:32:03Z")
By curiosity, what was the problem ? ---
**Author:** ![mhoeft](https://avatars.discourse-cdn.com/v4/letter/m/9dc877/32.png) [@mhoeft](https://lookmumnocomputer.discourse.group/u/mhoeft)\ **Post date:** [March 21, 2021, 7:52pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/9 "2021-03-21T19:52:37Z")
I assume an error in build quality, since this was my first project. I ended up just rebuilding the core module from scratch. Just happy I didn’t fry my CEM 3340 IC. I also ran into an issue where my standoff bracket was shorting between the power rails 🤦‍♂️ I guess you still have to be careful even if it’s anodized. ---
**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:** [March 21, 2021, 8:07pm UTC](https://lookmumnocomputer.discourse.group/t/troubleshooting-first-build-cem3340-simple-1v-oct-vco/2256/10 "2021-03-21T20:07:51Z")
> [@mhoeft](#): > > I also ran into an issue where my standoff bracket was shorting between the power rails generally we make some cut traces on the stripboard to isolate them from the circuit like that ![active real ring modulator stripboard by sound bender copie](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/b/b933e87769c9bdd97e9baa45af5e7d2d37934dfe.png)