Help making the 'My first VCO' module with the CEM3340

No, you should not expect anything useful from measuring the red dots. The control voltages should be measured from the other ends of the resistors as shown in the Annotated Simple 1V/Oct Oscillator Stripboard link I posted above. There are two control voltages, the CV Input one and the one produced by the tuning knob, each with its own 100k resistor. Measure them separately. The sum of these two voltages is what determines the pitch, and should be up around +9 V.

It’s also not very useful to stick a voltmeter on the triangle (or square, or ramp) outputs, either, because these are or should be oscillating at audio frequency. Better to use a scope to look at them, or lacking a scope use an audio probe:

That would tell you at least whether the 3340 is producing a tone that’s not getting to the output or not, which would help isolate the problem.

1 Like