What the crap?

Posted: 10/21/2007 6:13:47 PM

Joined: 10/13/2007

I didn't put this in my last topic, because it isn't about making my theremin anymore.

See, my theremin is working fine except for one thing: the closer I am to the pitch antenna, the DEEPER it is. Something is very, very wrong.
Posted: 10/21/2007 6:25:14 PM

Joined: 10/13/2007

Nevermind, but the problem has changed: if there's even the slightest vibration on the theremin itself, such as tapping the table it's on, the pitch shoots up and doesn't go back down unless I prod either C19 or C20.


They're the two blue things in this image on the bottom side of the board.
Posted: 10/21/2007 7:50:24 PM
RS Theremin

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

My first guess is D2 and especially D3 are not properly soldered to the board and the component lead is touching intermittently. C20 & C19 would cause excessive hum sound in your pitch if they were a problem.

That pitch sound going lower as you approach the antenna is a normal behavior fixed by minor pitch centering by adjustment of one of the coil slugs after the antenna and earth ground are hooked up properly. Find it in your manual.

Crap is the US dollar vs. the Euro.
Posted: 10/21/2007 7:57:41 PM

Joined: 10/13/2007

Well, D2 and D3 seem perfectly fine to me, but they also fix the pitch when pressure is applied.

What should I do to fix?
Posted: 10/22/2007 3:31:15 AM

From: Fresno, California USA

Joined: 3/26/2006

Maybe a bit more solder and heat on each connection will do the trick. Maybe you need to desolder and resolder. For desoldering I find desoldering braid (a tape of woven copper) works pretty well--press it onto the solder to be removed with the soldering iron and it will (shortly) draw up the solder. HOWEVER--don't use too hot an iron; 30 watts is really pushing it, 15 is OK. And diodes are among the more heat-sensitive parts; attach a heat sink (a little aluminum squeezy gizmo) between the diode proper and the place your are applying or removing the solder, and be quick about the soldering. Inspect joint carefully afterwards with a strong hand lens. In fact, maybe do it first. HTH
Posted: 10/22/2007 5:36:00 PM

Joined: 10/13/2007

Apparently, the problem was another torn wire.

You must be logged in to post a reply. Please log in or register for a new account.