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Help me troubleshoot my simple CD40106 VCO build
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Help me troubleshoot my simple CD40106 VCO build
valar modulis
First of all: I'm a complete noob and am in way over my head here. I've decided to build my own modular, with as much DIY as at all possible. Only problem: I have very little electronics experience. Headache ahead, I'm afraid wink

So for my first module I've decided to build a VCO, namely this old design

and have managed to breadboard it with exp input which seems to work just fine.
After having transferred it to vero-board nothing seems to work, however.
The issue seems to start around the 2N3904 in the expo-circuit. In the working circuit I measure around 5-6V between pin 1 and 3 of the transistor, while it's around 12V on the non-working circuit. Likewise there is a similar difference between pin 1 and 2 of the 40106 (5-6V for the working vs 12V for the non-working circuit).
I really can't wrap my head around what's the issue and have checked multiple times if the two circuits are identical, but can't find my mistake.

Does anyone have an idea for me on what to check for?
Any help is much appreciated smile
valar modulis
Never mind. I found a bridge between two strips on the vero board and cleaning that up solved it smile
Spivkurl
valar modulis wrote:
Never mind. I found a bridge between two strips on the vero board and cleaning that up solved it smile


That was going to be my suggestion yesterday, but I figured that you would probably find the issue. Happy that you did!

I've had this problem with veroboard quite a bit, even more than protoboard I would say. Except for all of the cool already designed vero layouts, I find it frustrating.

40106 is a fun chip though. I was just making clock VCOs and VCLFOs from this for a circuit bending project. I love that it can reach the MHz range with the right components.
masterofstuff124
wait.
can i get 6 VCOs out of one 40106 that have basiv 1v/oct? imma need to try this today!
valar modulis
masterofstuff124 wrote:
wait.
can i get 6 VCOs out of one 40106 that have basiv 1v/oct? imma need to try this today!

As I understood it you shouldn't go for more than 4 since oscillators will bleed into adjacent pins on the chip. Using the four corners triggers should be okay though
Spivkurl
Yep, for use in a module, the most I've seen is four per chip. This was not for exponential use either. Your mileage may vary.

I've been using it for more linear purposes. Definitely an easy way to make a utility VCO. For audio range stuff, I tend to like the feel/sound of the 4046.
masterofstuff124
Is this the correct way to add the trimmer?

https://imgur.com/a/kuYMFok
Grumble
I think that placing a potmeter in series with R7 is not a good idea, since it not only effects the gain but also the offset.
Prolly placing a trimmer in series with R11 would be a better choice since it will only effect the gain, use a trimmer of 500 ohms or maybe less.
masterofstuff124
luckily I have 4 Osc on one chip for this first PCB so I will try multiple configurations and report my findings. Thanks! nanners
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