RCA Theremin Service Notes

PART I – SERVICE DATA

(1) INSTALLATION

The necessary instructions for installing the RCA Theremin are contained in the instruction book that accompanies each instrument. The notes on location with regard to metal objects and all other points should be carefully checked. as satisfactory operation depends on correct installation.

(2) NORMAL OPERATION

Normal operation of the RCA Theremin may be checked in the following manner:
(a) Place the Theremin in operation by turning “On” the operating switch, turning the “Play-Off” switch to “Play” and making sure the rear doors are closed.
(b) Stand erect directly in front of the Theremin so that the body is at a distance from the cabinet determined by placing the right arm straight out from the shoulder with the hand closed. In this position the hand should just reach the pitch control rod.
(c) Now pull the right arm back to the shoulder. The Theremin should just approach zero beat in this position when the pitch adjustment condenser is at its mid-position. If zero beat is not obtained adjust the pitch adjustment until it is obtained with the hand in this position. Now extend the hand until it is one inch from the pitch antenna. At this point a note of from 1100 to 1400 cycles should be obtained. This may be checked with a piano. C sharp, two octaves above middle C is 1096 cycles and F sharp, two octaves above middle C is 1463 cycles. If these conditions are not fulfilled or the pitch adjustment condenser is not in the center, adjust a, described in Part I, Section 4.
The volume control may be checked as follows:
(a) With the Theremin in operation and an audible note obtained, a good loud signal should be obtained with the hand entirely removed from the volume control loop and the volume control adjustment at maximum (To the right). Placing the hand close to the volume control loop should reduce the volume and give complete cut-off when the hand is three inches above the loop and the volume control adjustment is at maximum. If cut-off is not obtained until the hand is closer or at a greater distance, an adjustment such as described in Part I, Section 3, must be made.