Moog Music Forum

Ive had this theremin for a few years and has never left the house. A few months ago it stopped producing sound. I opened it up and checked all of the solders and everything appears to be golden. When I plug it into an amp and turn it to 10 i can hear a very faint sound which responds to pitch modulation. Should i start circuit testing or does anyone know where i should look first?

I am not an expert on theremins, but seeing as no one else is answering, I'll give it a shot. I was a radio tech in another life, and theremin circuits are very similar to superheterodyne radio circuits, so I am familiar with the concepts of how these circuits work.

If you are at all unsure of how inductive/capacitive circuits operate, how hand capacitance can affect tuning these circuits, or are not sure about following procedures in a service manual, then attempting to fix this yourself could make things worse.

So, moving on...

If you're able to hear pitch differences, then the pitch reference and pitch variable oscillators appear to be working, as does the mixer circuit.

The fact that you can still hear some output tells me that the volume oscillator circuit might be out of adjustment. If you have a service manual for your theremin, check to see if it contains a procedure for tuning the volume oscillator. If it does, then performing the tuning procedure might bring the theremin back to life!

Otherwise, I would contact the manufacturer for service, as unless you are adept at troubleshooting circuits at the component level, I don't think there is really anything else you should attempt on your own.

HTH

Thanks, i will check it out.

Please let us know how you make out with that.

Good luck!

another problem could be just that you have it plugged in through a pedal whose battery is dead, or that blew your amp. You've probably already thought of these, just mentioning them just is case.

Tried all of this things, still doesnt produce. what can i do???

Did you ever figure this issue out?
I am having the same problem.
My Theremin worked the last time I played it, over a year ago, now the output volume is very very low.
It is on a mic stand not near anything, and I have tried 2 different amps that both pass signal with other instruments connected to them.


Thanks,
Benjamin

I bought a standard etherwave last week. It worked fine for a bit then went very quiet. Pitch and volume antenae still work but I now need my amp on 10 when it was OK on 1 before. I've tried different leads and different amps but my conclusion is that the Etherwave output has seriously reduced. Any ideas?

robotboy wrote:Did you ever figure this issue out?
I am having the same problem.
My Theremin worked the last time I played it, over a year ago, now the output volume is very very low.
It is on a mic stand not near anything, and I have tried 2 different amps that both pass signal with other instruments connected to them.


Thanks,
Benjamin

My friend's standard Etherwave was behaving just as described in this thread. We discovered that diode D1 was dead conducting both ways. Now it's working again.

Hope this is useful to someone.

Thanks Avant. I've sent it to Source, the Moog UK service centre, and will report back.

Best wishes

Hello,
I have the same problem! Very faint pitch modulation sound in background.....
If It's the diode that died, can someone point out where it's at? or a schematic maybe?
Would be great...

This happened to mine as well. I was away for about a year without it and when I came back and tried it out, it made no sound. I cranked the amp to see if I could hear anything and when I turned it on I could hear the pitch wobble in frequency very quickly as it powered on and then it sustained at a constant frequency for a while at a very, very low volume. I thought it had something to do with my volume antenna but I couldn't imagine what.

Truth is, I'm actually trying to sell the sucker, and this is putting a large kink in that operation.

There is an unofficial service point for theremins in Western Europe which has lots of experience in fixing Etherwaves. Contact me if you're interested.