CEM3340 breadboard help - it squeals!

Hi, I breadboarded the CME3340. I get a signal when connecting Triangle and Saw but not what is expected: a constant high pitch squeal when I turn the trimmer close to maxiumum. The Beatstep pro supplies the CV input from V/OCT pitch and makes some subtle change to the tone but nothing like note change.
NB: This is the Coolaudio V3340 chip and I checked the datasheet which is exactly the same as the CEM3340. I’m using Uzeus eurorack power to supply -12v, GND, +12v.

Any thoughts?

I assume this type of trimmer is okay for this.

You need a multiturn trimmer. Also, why use two breadboards? The ICs can be placed in the middle of one board and save all those unnecessary jumper wires that could be a cause of trouble (improper contact, disconnected as you move this around, etc).


A mutliturn trimmer, okay I have one of these. The reason I have used two breadboards is because the circuit is too wide to fit on one breadboard. It seems there aren’t wider pin breadboards so this was my solution.

These ICs are meant to fit in the middle of these breadboards. You only think that it doesn’t because the IC is brand new. The legs need to be bent very carefully just a tiny little bit to fit. It would be exactly the same if you’d try to fit the IC into its respective socket. It takes a little bit of wiggling the first time. Just start again with one breadboard, fewer jumber wires, and a multiturn trimmer and see if you can replicate the problem.

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The trimmer in top left is missing the jumper to the resistor to pin 1 of the 3340


This circuit is too wide to fit one on breadboard, believe me I tried it. It needs 8 points on the left and 13 on the right. A single breadboard only gives you 5 points on each side and when you have the IC in the middle that’s only 4 points on either side.

It is in line, it just looks lie that because of the angle. The top left leg connects to the white wire, resistor and purple pot signal wire on the other side. I think it’s working properly, I just need to use a multiturn trimmer, waiting for arrival by post.

Okay, I misunderstood you. Still. Do you really need 13 breadboard points on each column of the breadboard for this circuit? Even if you do, you can fit them in one breadboard. Here is an example:

Easy. 15 usable points out of an IC pin. All the points in columns 8 to 12 connect to IC1 pin 5.

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It absolutely is possible to build even a much more complex 3340 circuit on a single breadboard. I’ve done it.


I’m sure it’s do-able but it’s more work and then harder to read and reference the original design. I did think of that.
Anyhow it’s not the problem I even asked about. I plan to prototype it on pcb and wanted to breadboard it in the quickest and easiest way possible.

You don’t need the multi turn to make it work. It is helpful for volt per octave tuning but still not necessary for general operation. Although the problem could just be a faulty potentiometer. Either way you should have two legs of the pot connected to each other connecting to pin 3 as well as through a resistor to pin 2, and the remaining leg through a resistor to pin 1. Can you snap another pic from a better angle? I’m just having trouble understanding your description with the limited angle.

Indeed. I have had issues with nearly everything in the past, from fake ICs to faulty multiturn trimmers. Can you check all the components with a multimeter to see if they are okay?

I also found that problems in the breadboard arise from faulty or missing connections. That’s why I try to keep jumper cables to a minimum, and the components fairly close by.

If everything else is accounted for, you could take a few voltage measurements at the IC pins to pin point the problem.

Is ground from the Beatstep connected to ground on the breadboard?