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 Theremax DIY case/enclosure guidelines 
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Joined: Sun Nov 09, 2008 2:49 pm
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Post Theremax DIY case/enclosure guidelines
Theremax, custom case?

It is OK to build the kit, apply power and tune and test the operation, spread-out on a piece of wood, cardboard, or plastic. Even without antennae it should tune and respond to your hands moving to or
from the ends of the antenna cables. Then put in a case like is shown in the assembly instruction manual with wood panels, a metal front-panel and an aluminum base and with the antennae attached in their clamps it will tune and operate as intended. But, if you have metal near the antennae, it will work to couple them to each other, or, to ground if the metal has a connection with the circuit board point G (0vdc/ground/circuit-common).

In our kit, the board is placed up off a metal (aluminum) case-bottom via the #4-40 mounting screws/nuts and 3/16" spacer (about 4mm). A solder eyelet is under the nut at one corner of the board with the power supply minus pole and wire G (and the panel LED ground wire) which puts this whole bottom at zero potential or ground/circuit-common. This works as a local load to the four oscillator circuits and helps stabilize them somewhat. The metal front-panel being grounded or not is not so important, but circuit board wire SG goes to the panel connectors and controls joined by a solid-bare wire. The case bottom and panel are keep away from the antennae and mounts. The case bottom is closest at about 3" or 7-8cm.

If the panel with the antennae mounts is metal, the antenna lead must pass through a hole that is about 1/4" or 5mm and then the closest the clamp or antenna can be to the metal is about 1" or 2-3cm. The material for the antennae is not so critical. We have used copper for them, but now use brass. I have seen units in for service where the builder has elected to use aluminum rods and these were OK--also plumbing fittings.
The loop for the volume antenna is to concentrate the field and the affect the hand has on the field. It is better to not have to move the volume hand so much. Then, it is easier to hold a steady pitch with the
other hand. A plate or a spiral can be used too. I built mine into a red, plastic pencil-box. I used a tray to mount the board and controls, pushed the hot iron through the box to allow the control shafts to extend through, mounted a 9pinD connector for the power, controller, and audio connections, and RCA phono connectors for the antenna mounts. These
connectors didn't turn out to work so well as the antennae twist in the connector with metal rods in them, but they're OK with the lengths of red insulated wire I have in place now. They're each formed into spirals.

Below is a link to a photo of a completed kit and front-panel assembly showing the way the wires should be smoothed, formed and routed to be away from the parts in the four oscillator circuits and the antennae cable ends. ... Repair.JPG

This is my compact Theremax: ... 505sc1.JPG ... 505sc2.JPG

Scott Lee

Fri Nov 19, 2010 10:59 am
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