# 3340 VCO sounds like a LFO, please help me! **URL:** \ **Category:** DIY STUFF\ **Created:** [July 27, 2020, 2:45pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521 "2020-07-27T14:45:31Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![THOGRE](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/thogre/32/5189_2.png) [@THOGRE](https://lookmumnocomputer.discourse.group/u/THOGRE)\ **Post date:** [July 27, 2020, 2:45pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/1 "2020-07-27T14:45:31Z")
Hello, my 3340 VCO behaves like an LFO, if I connect my beat step and set the octaves very high, the tone will also be a little higher, but not as it should be. So I think he’s getting too little power somewhere. Where can I start to solve the problem? Here is the layout after I have built. ![alfa4VCO Wannenstecker_ final-fürLMNC Forum](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/0/05d5ec08eaed631748fa10bfccbd6882671e007c.jpeg) ---
**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, 3:06pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/2 "2020-07-27T15:06:27Z")
I assume you tried adjusting the trimmer? ---
**Author:** ![THOGRE](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/thogre/32/5189_2.png) [@THOGRE](https://lookmumnocomputer.discourse.group/u/THOGRE)\ **Post date:** [July 27, 2020, 3:31pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/3 "2020-07-27T15:31:47Z")
Yes i did 🙂 its fully “open” ---
**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:** [July 27, 2020, 3:44pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/4 "2020-07-27T15:44:53Z")
Your coarse tuning pot may not be wired up correctly. See the drawing and the first few comments here for how and where to measure the CV inputs: > [@Annotated Simple 1V/Oct Oscillator Stripboard](https://lookmumnocomputer.discourse.group/t/annotated-simple-1v-oct-oscillator-stripboard/1267): > > And here’s [the LMNC 3340 stripboard layout](https://www.lookmumnocomputer.com/projects#/cem-3340-diy-simple), with scribbles: See [here](https://lookmumnocomputer.discourse.group/t/annotated-simple-low-pass-filter-stripboard/1266) for the annotated Simple Low Pass Filter stripboard. ---
**Author:** ![THOGRE](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/thogre/32/5189_2.png) [@THOGRE](https://lookmumnocomputer.discourse.group/u/THOGRE)\ **Post date:** [July 27, 2020, 5:01pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/5 "2020-07-27T17:01:58Z")
I have now measured all the points you marked. Wherever + 12v should be, I have +11.63 as my PSU outputs it. On the internal CV I have +11.63 with the potentiometer turned on and with the 0V closed I exchanged the 1nF oscillator capacitor. I don’t know what to do next ---
**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 27, 2020, 5:29pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/6 "2020-07-27T17:29:43Z")
you are not mistaken in resistance values ​​somewhere ? maybe test it with multimeter ? ---
**Author:** ![THOGRE](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/thogre/32/5189_2.png) [@THOGRE](https://lookmumnocomputer.discourse.group/u/THOGRE)\ **Post date:** [July 27, 2020, 5:32pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/7 "2020-07-27T17:32:07Z")
I’m checking that right now, the as3340 isn’t broken either, it works just fine in my other VCO. I hate being so helpless ☹ ---
**Author:** ![THOGRE](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/thogre/32/5189_2.png) [@THOGRE](https://lookmumnocomputer.discourse.group/u/THOGRE)\ **Post date:** [July 27, 2020, 6:10pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/8 "2020-07-27T18:10:12Z")
Its working now !!! @Dud you were right ! Now it works! I used a 1.8k instead of the 24k. I made a mistake in the colors. Finally, my second VCO one step closer to good sounding music. Thank you all for the quick and good help. You are the best ! ---
**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 27, 2020, 9:29pm UTC](https://lookmumnocomputer.discourse.group/t/3340-vco-sounds-like-a-lfo-please-help-me/1521/9 "2020-07-27T21:29:13Z")
super ! happy for you 😃