# 1222 Tuner VCO Module **URL:** \ **Category:** KOSMO MODULES\ **Created:** [January 17, 2020, 5:33pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16 "2020-01-17T17:33:40Z")\ **Posts on this page:** 20\ **Page:** 17
**Author:** ![KardashevTypeII](https://avatars.discourse-cdn.com/v4/letter/k/43a26b/32.png) [@KardashevTypeII](https://lookmumnocomputer.discourse.group/u/KardashevTypeII)\ **Post date:** [September 2, 2020, 9:35pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/324 "2020-09-02T21:35:03Z")
Stefan, They say nobody beats the Biz. Apparently in this case the Aiz beats the Biz. -Fumu / Esopus ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 26, 2020, 5:37am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/325 "2020-09-26T05:37:39Z")
I have a new gremlin that showed up a couple weeks ago. After a certain amount of time, all three oscillators in my top row start wobbling (almost like a fast LFO is connected to the pitch). Have any of you experienced this? Details: - it happens to all three at once - it does not happen to the oscillator in the bottom case - they are wobbly even when I completely remove any cables from the bottom case - the most recent modules I added to the top case were the Midimuso and the rotary phone module - I tested the pitch with and without any cv inputs and it still wobbled which rules out the midi to cv module as a potential cause (as far as the cv goes) - neither the wall wart or power supplies seemed that warm The next time it happens I will double check the temperature of the power supplies and wall warts. I will note how long it takes to happen. I also plan to remove modules one at a time once it happens to see if one of the other modules might be the cause. ---
**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:** [September 26, 2020, 6:18am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/326 "2020-09-26T06:18:08Z")
That does sound to me like it might be a power issue. With no CV plugged in, that seems the most likely source of a problem common to all three. Have you [measured the current draw](https://lookmumnocomputer.discourse.group/t/ribbon-cable-tester/1600/29) of the phone module? Has anyone measured the current draw of the MidiMuso? ---
**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\ **Post date:** [September 26, 2020, 6:23am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/327 "2020-09-26T06:23:44Z")
It’s got to either be the power supply itself, or something causing ripples in the power supply output. A dual trace scope on the supply lines should show this. ---
**Author:** ![Vumnoo](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/vumnoo/32/6942_2.png) [@Vumnoo](https://lookmumnocomputer.discourse.group/u/Vumnoo)\ **Post date:** [September 26, 2020, 12:07pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/328 "2020-09-26T12:07:18Z")
Swap one at a time from the top cabinet into the lower cabinet. Will help you figure out if it’s a module or the cabinet/psu ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 26, 2020, 4:46pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/329 "2020-09-26T16:46:42Z")
Okay. So. It’s somehow midimuso related. More notes: - The wobble came back almost immediately when powering up this morning. - Once I removed the Midimuso, the oscillators became stable. Will shift the conversation to that thread when I know more. ---
**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:** [September 26, 2020, 9:57pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/330 "2020-09-26T21:57:51Z")
Mine have been doing the same thing on and off. I just tried unplugging the MIDImuso, but it doesn’t seem like it makes a difference. What’s happening is that the reference voltage is unstable. Here’s a video: [![](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/4/457b522843696e763be64fdb2e2e8df910871a0b.jpeg "Performance VCO Drift") ](https://www.youtube.com/watch?v=K2ONag_U-LQ) EDIT: I now unplugged everything but the VCOs and they’re behaving the same way. One more than the other. ---
**Author:** ![antoine.pasde2](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/antoine.pasde2/32/326_2.png) [@antoine.pasde2](https://lookmumnocomputer.discourse.group/u/antoine.pasde2)\ **Post date:** [September 27, 2020, 12:12am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/331 "2020-09-27T00:12:40Z")
> [@ChristianBloch](#): > > What’s happening is that the reference voltage is unstable. Could it be related to this ? > [@1222 Tuner VCO Module](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/203): > > I finally got around to powering up my #1222 VCOs, I was waiting for the mica caps to arrive from AliExpress but they’re still at least a couple weeks away, so I gave up. While poking around trying to figure out why I can’t seem to be able to calibrate the frequencies (more on that later), I noticed a resistor getting quite hot. It is R42, the resistors in series with the 4.1 voltage reference. I did a bit of math : The current through R42 is I=V/R= (12-4.1)/220 = 35.9mA which seem… ---
**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:** [September 27, 2020, 3:43am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/332 "2020-09-27T03:43:04Z")
Hmm, not a bad guess. Let me check that out. ---
**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:** [September 27, 2020, 3:57am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/333 "2020-09-27T03:57:28Z")
Well, will you look at that: ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/1/1081fb0c22dc127aa4f36ce9d89b33cac371fc98.jpeg) I put in a 1K and it’s stable. I measured the resistance of the 220R I removed, but it still measures 220, so I don’t know if it could be burned out. In any case, fingers crossed that the reference voltage stays stable. ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 27, 2020, 5:14am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/334 "2020-09-27T05:14:15Z")
Let me know please. If so, I’ll do the same thing next week. ---
**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\ **Post date:** [September 27, 2020, 6:43am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/335 "2020-09-27T06:43:19Z")
May be worth a sticky at the top if it fixed it, or it’s own short thread… ---
**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:** [September 27, 2020, 7:45am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/336 "2020-09-27T07:45:50Z")
Yeah, still solid several hours later. ---
**Author:** ![twinturbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@twinturbo](https://lookmumnocomputer.discourse.group/u/twinturbo)\ **Post date:** [September 27, 2020, 8:48am UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/337 "2020-09-27T08:48:05Z")
Cool, @Hackseven , give it a try and if it solves the problem ---
**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:** [September 27, 2020, 12:32pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/338 "2020-09-27T12:32:07Z")
Did you replace the resistor on all oscillators? The Truly Scientific Test would be to just replace one and see if its behavior changes while the others don’t. But this does look promising. I do think @lookmumnocomputer should update the schematic/bom with a 1k resistor. ---
**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:** [September 27, 2020, 2:16pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/339 "2020-09-27T14:16:25Z")
I did replace both, but the other module was mostly stable anyway. Would just go wobbly every now and then. ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 27, 2020, 2:22pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/340 "2020-09-27T14:22:55Z")
I’ll try that this afternoon. ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 27, 2020, 6:24pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/341 "2020-09-27T18:24:23Z")
Alrighty. Science results: - I put the Midimuso back in (to get the wobble back) - When the oscillators started wobbling, I replaced the 220R with a 1K on only one of three. - All three still wobble (even the oscillator with the new 1K resistor. I could try swapping it on the others in case the unstability bleeds to other modules somehow. ---
**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:** [September 27, 2020, 6:29pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/342 "2020-09-27T18:29:25Z")
I think we probably had different problems that just happened to manifest the same. It could be that the MIDImuso draws enough power to push your power supply past the limit. What happens if you unplug several other modules but not that one? ---
**Author:** ![heckseven](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/heckseven/32/23483_2.png) [@heckseven](https://lookmumnocomputer.discourse.group/u/heckseven)\ **Post date:** [September 27, 2020, 7:22pm UTC](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/343 "2020-09-27T19:22:04Z")
Seems like it might be a power supply issue of some sort. - I left the midimuso in and removed other modules one at a time. Each LFO I removed decreased the wobble slightly. - I tried different wall warts. I even swapped for one that was only 1amp instead of two which lowered the pitch and increased wobble. This seems promising. I use two FC Microbus power supplies per case connected [in parallel](https://lookmumnocomputer.discourse.group/t/power-supplies-choices/357/19) I think. Each case has one 12V 2a AC AC wart. Perhaps I need to get a better wall wart or explor other power supplies? Ideas? I suppose I could also separate the Microbus and have a wall wart per bus, but I was hoping to keep it to one power cord per case. [Previous page](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16.md?page=16) [Next page](https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16.md?page=18)