Pitch problems on Etherwave Theremin kit

I've just finished my Moog Etherwave Theremin (not pro) kit, and as far as I know I've followed the instructions, only materials not from the kit is my stain (minwax red mahogany) and the solder , but the pitch is messed up. Within two inches of the pitch antenna the pitch gets higher as you approach, at two inches there's no sound and beyond two inches the pitch increases you get farther away. I've played with the pitch knob enough with no results. Also probably part of the same problem, the pitch never gets really low like I've heard. Please help! I'm a young musician who has no electronic experience, but I want to use this awesome instrument in my band!

Also waveform knob doesn't seem to work and not sure if I'm getting full range within the 2 inches I have to play with. Really confused :/

same problem as http://www.thereminworld.com/forum.asp?cmd=p&T=4298&F=3

It seemed Gordonc had a solution but he never gave it:
"Pitch knob is all the way to the left

What happens when you stand facing the theremin with your right hand by your side and slowly turn the pitch knob to the right?

Doe the sound go down in pitch until it is very low and then become silent and then start to rise again? (If it does, I think I know what the problem is.)"

Hi robnybod. Welcome to Theremin World.

If the pitch knob behaved as I described when you are standing about an arm's length from the pitch rod, then the problem would be that your understanding of the function of the pitch knob was in error.

But - as the pitch knob does nothing in your case, I guess that is not the problem.

I have no idea why the zero beat zone (the silent area) is stuck at 2 inches from the rod no matter what you do with the pitch knob. I suggest checking all your solder joints (maybe you have inadvertently short circuited the pitch pot or something) while we wait for an expert to come along with a useful diagnosis.

Also - the effect of the waveform knob is most obvious on lower notes - probably best to worry about that once you are getting the full range of frequencies, not before.

This is the range of my etherwave...

http://dl.dropbox.com/u/1546794/etherwave%20sweep.mp3

(The step at about 31 seconds is where I touch the pitch rod.)

Thanks so much, Ill check all my connections tomorrow.

This behavior (zero beat zone at ~2inch from the pitch rod and almost not moving with the pitch knob) is normal for an Etherwave without cover since the latter comprises 9 hidden big metal screws whose parasitic capacitance has to be taken into account).

If this behavior persists even with the cover put onto the theremin, you have to do the following checks:
a) Did you screw the green cable to the aluminum foil below the wire which leads towards the pitch rod?
b) Take a multimeter, connect its black cable to the green wire on the audio output and check with its red cable if there are:
-> +/- 0V at the green wire of the pitch potentiometer,
-> -11V at the black wire of the pitch pot (if these are missing, neither pitch nor volume nor waveform adjusting will work)
-> a voltage which varies between the both values above when you turn the pitch knob at its blue wire.

Please let us know what voltages you found and we'll go further in the diagnostics.

Hi there

I have a similar problem. After finishing the assembly of the etherwave, I turned the theremin full of hope on, but all I hear is one steady, rather distorted tone (about 250 Hz). It always starts low, getting higher but then it gets stuck on that very note. Volume and Pitchknob don't seem to respond.

I checked with a multimeter, as you suggested Thierry, and it is:

-> +/- 0 at the green wire of the pitch pot

-> - 5.5 at the black wire

-> - 4.5 at the blue wire

 

I don't have much experience with such things, so I'm happy for any advice! :)

What do you guys think?

There is for sure either a wiring problem or a fault on the circuit board. There must be -11.3V at the black wire. Without correct power supply, nothing will work correctly.