I need theremin construction help. :(

Posted: 10/13/2007 9:47:54 AM

Joined: 10/13/2007

Okay, I bought a Moog Etherwave kit and I put it together, and now I can't get it to work.

All that comes out of the speakers is this really high pitched, quiet whine that I can silence with the volume antenna, but can't change the pitch of without using the knob, and even then it's negligable.

I know I didn't solder anything to the wrong port/whatever, because I've checked about 10 times. I also know that the paint I used was non-conductive. The main board is also probably not the problem, as I was very careful with it.

Did I just do a really bad soldering job? If so, can it be repaired? Does slight stripping on the outside of the compressor nut on the antennae do anything like this?

I hope this description is enough to help you help me.
Posted: 10/13/2007 2:07:13 PM

From: Massachusetts

Joined: 8/18/2007

The good news is that the volume beat oscillator
appears to be working. And since that is tha
more complicated section you are more than
halfway there.

Make sure that your solder joints have a shiny
appearance and not a dull appearance. Reflow
the solder joint if you are in doubt. It
almost seems like it is a bad connection.

Recheck the orientation of the components.

Try going through the tuning procedure again.

If you have access to a DMM and an oscilloscope
try the instructions I gave in the Theremin
Newcomers Forum thread "Uh oh ..."

(* jcl *)

Posted: 10/13/2007 3:27:21 PM

Joined: 10/13/2007

I'm pretty new at this, so can you explain what it means to "reflow" a solder joint? This was my first time ever trying that.
Posted: 10/13/2007 6:17:05 PM

From: Massachusetts

Joined: 8/18/2007

When the solder melts it flows. If you re-heat it

You should be able to press the hot tip of your
soldering iron against the solder joint.

(* jcl *)
Posted: 10/19/2007 5:08:31 PM

Joined: 10/13/2007


This is a video chronicle of what's still wrong.

I resoldered all the lugs and stuff.
Posted: 10/19/2007 6:27:39 PM

From: Massachusetts

Joined: 8/18/2007

Can you take some high resolution still pictures
of the PCB (expecially the pitch area)?

I am curious about the orientation of the pitch antenna inductors. It seems like it is different
than the EM Theremin.

It you have an ohm meter do you have continuity
between the pitch coils and the antenna?

(* jcl *)
Posted: 10/19/2007 6:55:35 PM

Joined: 10/13/2007

Please repeat what you just said in conventional layman's English so I can do what you said.
Posted: 10/19/2007 7:20:46 PM

From: Massachusetts

Joined: 8/18/2007

Take a picture of the circuit board with
your digital camera and post it.

Also if you have the Etherwave documentation
that shows the component placement on the
circuit board scan it and post it.

(* jcl *)
Posted: 10/19/2007 7:22:55 PM
Brian R

From: Somerville, MA

Joined: 10/7/2005

Hi, BeatlesLover--

"PCB" = printed circuit board

As for the continuity business: This means using an ohmmeter (or multimeter on its "ohmmeter" setting) to test whether two points are electrically connected, or not. If you don't have a multimeter, for heaven's sake run out and buy one. They're not expensive (I think I paid all of $20 for mine at Radio Shack, and there are even cheaper models out there), and they're invaluable in diagnosing electrical problems.

(And no, I'm not much more knowledgeable than you are... now that you mention it, I'm a bit of a disgrace to my father and his father, both electrical engineers.) :-)
Posted: 10/20/2007 1:30:27 PM

Joined: 10/13/2007

Right. Here's a dozen photos I snapped of the board and attachments.


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