Theremax construction project - 2

Posted: 1/9/2009 6:44:38 PM
omhoge

From: New York, NY

Joined: 2/13/2005

Continued from Theremax construction project (http://www.thereminworld.com/forum.asp?cmd=p&T=3660&F=3)
Posted: 1/10/2009 6:11:51 PM
npb

From: Columbia, MO

Joined: 1/10/2009

I am a "theremin newcomer" (and also, frankly, an electronics newcomer) who is trying to build a theremax. When I got the the point of plugging it in to my stereo, turning it on and trying to tune it I got nothing but the red light (not enough ground? - I plan to buy an amp for it but have not yet). I am looking at the previous threads and seeing that the problem may be that I built in in an aluminum case. (Though like a previous poster I did this after seeing on the PAIA website that this was OK as long as the antenna passed through the case without touching it). Does anyone have some suggestions on how I should troubleshoot this?

(I do not have an oscilloscope.) I am feeling sort of lost.
Posted: 1/10/2009 6:31:28 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

A metal (or any other conductive material) case will ALWAYS act as a big capacity which is seen first by the antennas since it is nearer to them than your hands ever may be.

Take your theremax out of its electromagnetic prison (It's a theremin, not a microwave oven!) and try the electronics first on a wooden table without case. This will make debugging easier if it will not start working in the first moment of freedom.

Let the Paia guys write what they want - just use your common sense and ask yourself why L. Theremin himself used wooden cases although he lived in the Tinplate Age.
Posted: 1/11/2009 5:41:02 AM
snuffy406

From: Maryland, USA

Joined: 12/13/2008

The copper foil peeled off nice and easy, and the 3M contact cement came off with a quick wipe of paint thinner. Thanks to everyone for the advice.
BUT, Scorch, for a wooden bottom, that 3M spray adhesive is very forgiving, just mask off where you don't want it, if you are gonna use foil for the ground plane. Sounds like you have a good deal going on the cabinet.
Posted: 1/11/2009 9:58:43 PM
npb

From: Columbia, MO

Joined: 1/10/2009

Thierry:

Thanks! It is out of its metal case and seems to be working!
Posted: 1/12/2009 1:39:15 AM
Thierry

From: Colmar, France

Joined: 12/31/2007

;-)
Posted: 2/13/2009 6:53:15 AM
snuffy406

From: Maryland, USA

Joined: 12/13/2008

[b]IT'S ALIVE![/b]
My Theremax came to life at 06:00 a.m. EST. I've got it tuned up with the supplied antennas, and it sounds right.

The antennas they give you are like heavy duty coat hanger wire, a hair less than 1/8" diameter.
As I've read on this site, the pitch response is far from linear. I'll be changing to antennas made from 1/4" O.D. copper tubing soon, and then going to a Lev pitch antenna. I'll post a link here to pictures of the whole mess in a few days.
Posted: 2/26/2009 3:38:21 PM
snuffy406

From: Maryland, USA

Joined: 12/13/2008

Pictures of the Theremax, working but still being modified. Cabinet is finished and looks lovely.
link (http://www.flickr.com/photos/15226899@N07/3308093935/)

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