Problem with EM-theremin: non-functional volume antenna circuit and volume oscillator/tuning

Hi,

We are two students building an etherwave theremin but are facing some problems with the volume oscillator. We are using the schematics from this paper http://www.suonoelettronico.com/downloads/HotRodEtherwav.pdf and uses the instructions from this article http://www.cs.nmsu.edu/~rth/EMTheremin.pdf .

As of now, we are not able to get everything functional and are not sure why. We have at least isolated the problem to the volume oscillator and the volume antenna circuit by inserting an artificial signal from the volume antenna (at R14) and found the vca, vca processor and pith oscillator functional (we could control the pitch with the antenna and the volume with the artificial signal). Have anyone stumbled upon the same problem or knows what the problem might be?

KevKri said: We have at least isolated the problem to the volume oscillator and the volume antenna circuit by inserting an artificial signal from the volume antenna (at R14) and found the vca, vca processor and pith oscillator functional (we could control the pitch with the antenna and the volume with the artificial signal). Have anyone stumbled upon the same problem or knows what the problem might be?

If you etched your own pcb then inspect it with a magnifying glass. Is the volume oscillator oscillating Q6 & Q7, what frequency do you measure?

Is D1 in the proper direction?

My best three guesses, so good luck!

Christopher

Thanks for your tips Christopher, we have now had time to check these, and other things. The volume oscillator is oscillating at 480kHz (it should be 450kHz) and D1 is orientated in the right direction.

We have found that we don’t get the correct voltage at D1, it should be -3V, but we only get -0,52V. Could this be the problem of why the artificial signal worked but the volume oscillator does not.