The fridge killed my theremin!!!

15 DCV will be right for all tests I described up to now.

If your multimeter is analog, you'll have to reverse the red and black lead in order to check negative voltages. If it's digital, it will indicate them correctly with a minus sign without reversing the leads.

It's reading the +12 and -12 volts fine but I can't figure out which pin is 12 on U3. Do I keep the black lead on the ground?

U3 has 8 pins (#1 to #8) on the left side, #1 being near the "nose" of the chip which points towards the rear side of the theremin, and 8 pins (#9 to #16) on the right side in reverse order, so that #16 is nearest to the "nose".

This should allow you to count and find #12.

All measurements are vs ground, so let the black lead there.

Ha, I don't know if I'm doing it right but I have an analog meter so it was trying to go in the negative and wouldn't be able to go further. I reversed the leads and it read in between 7 when my hand was far away and 10 when it was touching. That's what it read on the AC15V chart, I guess it could be somewhere between 400 and 600 DC Vma too. I don't really know what chart on the meter to read. It reminded me though, that a while back I discovered that when I would try and turn the volume knob down, the volume wouldn't shut off completely. So, maybe it was been on it's way to breaking down.

First thing: The volume knob does NOT adjust the output volume, but the response of the volume field around the loop.

Second thing: A reading between (-)4 and (-)7 Volts shows that the volume oscillator is working but most probably not in a correct manner. Please try to repeat your measurement with the volume knob set to center position.

Yeah, it goes from just below 500 mA to just over 600 mA DC. Is that normal? It also buzzes quite a bit when I plug it in.

No, that's not normal.

The next step would be a try to retune internally the volume oscillator section. Either this will correct the problem or it will clearly indicate another source of the problem.

But, without wanting to offend you, I'm afraid that this should be done by someone who is more experienced in electronics because there is a big risk to worsen the situation. Let us know where you live and we'll try to find one of the more technical forum members in your neighborhood who could help you directly or someone to whom you may send it in.

I would be ready to repair it without cost (out of shipping and eventual spare parts) if you are ready to send your theremin to France. But perhaps we'll find someone who is nearer to you.

No worries, I'm in Vancouver, Canada. Thanks for all the help so far, it's nice to have someone help out.

Let's hope that we'll find someone in your neighborhood. You could naturally send your Theremin to the Moog plant, but I fear that they will ask traditionally for a lot of money.

If you think that you prefer getting it fixed by me, just send me an email to theremin(at)tfrenkel(dot)com .
In that case you would only have to send me the "nude" theremin without antennas and power supply (all present here).